Merge lp:~blake-rouse/maas/vlan-relay into lp:~maas-committers/maas/trunk

[Blake Rouse]

Support the ability for a VLAN to act as a relay for another VLAN.

[Blake Rouse (blake-rouse)]

I have tested this and the dhcpd.conf is getting written correctly. Still waiting on review from design before landing.

[Mike Pontillo (mpontillo)]

Looks good; I have a few questions and comments below before this lands.

Don't we also need a validation to ensure you cannot enable DHCP on a VLAN with a relay?

review: Needs Information

[Mike Pontillo (mpontillo)]

Also, can you link bug #1602412 to this branch with --fixes?

[Blake Rouse (blake-rouse)]

> Looks good; I have a few questions and comments below before this lands.
>
> Don't we also need a validation to ensure you cannot enable DHCP on a VLAN
> with a relay?

I did not want to block this. So if they enable DHCP it clears the relay_vlan and shows a warning in the UI when they go to enable.

[Blake Rouse (blake-rouse)]

I am not making that change in my branch. That is not even related to the
change I am making. File a bug if its causing an issue.

On Wed, Nov 30, 2016 at 4:14 PM, Mike Pontillo <email address hidden>
wrote:

>
>
> Diff comments:
>
> >
> > === added file 'src/maasserver/migrations/builtin/maasserver/0095_set_
> default_vlan_field.py'
> > --- src/maasserver/migrations/builtin/maasserver/0095_set_default_vlan_field.py
> 1970-01-01 00:00:00 +0000
> > +++ src/maasserver/migrations/builtin/maasserver/0095_set_default_vlan_field.py
> 2016-11-30 16:44:24 +0000
> > @@ -0,0 +1,24 @@
> > +# -*- coding: utf-8 -*-
> > +from __future__ import unicode_literals
> > +
> > +from django.db import (
> > + migrations,
> > + models,
> > +)
> > +import django.db.models.deletion
> > +import maasserver.models.subnet
> > +
> > +
> > +class Migration(migrations.Migration):
> > +
> > + dependencies = [
> > + ('maasserver', '0094_vlan_relay_vlan'),
> > + ]
> > +
> > + operations = [
> > + migrations.AlterField(
> > + model_name='subnet',
> > + name='vlan',
> > + field=models.ForeignKey(to='maasserver.VLAN',
> default=maasserver.models.subnet.get_default_vlan,
> on_delete=django.db.models.deletion.PROTECT),
>
> Ah, my mistake. But I think there might still be an issue here, just not
> exactly where I pointed it out.
>
> According to the Django docs, CASCADE is the default when no `on_delete`
> option is set. Wouldn't that cause severe unintended consequences in the
> case of the `relay_vlan` field? I think we should use `on_delete=SET_NULL`
> on the `relay_vlan` field.
>
> > + ),
> > + ]
>
>
> --
> https://code.launchpad.net/~blake-rouse/maas/vlan-relay/+merge/312165
> You are the owner of lp:~blake-rouse/maas/vlan-relay.
>

[Blake Rouse (blake-rouse)]

Ah thanks for clarifying. I have fixed the issue and included a test to check.

[Mike Pontillo (mpontillo)]

Thanks for the fixes. I found one other issue below; please at least fix the text. I'll leave it up to you what action to take in that scenario.

review: Approve

=== modified file 'src/maasserver/api/tests/test_vlans.py'
--- src/maasserver/api/tests/test_vlans.py	2016-05-24 21:29:53 +0000
+++ src/maasserver/api/tests/test_vlans.py	2016-12-06 08:04:41 +0000
@@ -84,6 +84,29 @@
         self.assertEqual(vid, response_data['vid'])
         self.assertEqual(mtu, response_data['mtu'])
 
+    def test_create_with_relay_vlan(self):
+        self.become_admin()
+        fabric = factory.make_Fabric()
+        vlan_name = factory.make_name("fabric")
+        vid = random.randint(1, 1000)
+        mtu = random.randint(552, 1500)
+        relay_vlan = factory.make_VLAN()
+        uri = get_vlans_uri(fabric)
+        response = self.client.post(uri, {
+            "name": vlan_name,
+            "vid": vid,
+            "mtu": mtu,
+            "relay_vlan": relay_vlan.id,
+        })
+        self.assertEqual(
+            http.client.OK, response.status_code, response.content)
+        response_data = json.loads(
+            response.content.decode(settings.DEFAULT_CHARSET))
+        self.assertEqual(vlan_name, response_data['name'])
+        self.assertEqual(vid, response_data['vid'])
+        self.assertEqual(mtu, response_data['mtu'])
+        self.assertEqual(relay_vlan.vid, response_data['relay_vlan']['vid'])
+
     def test_create_admin_only(self):
         fabric = factory.make_Fabric()
         vlan_name = factory.make_name("fabric")
@@ -182,6 +205,23 @@
         self.assertEqual(new_vid, parsed_vlan['vid'])
         self.assertEqual(new_vid, vlan.vid)
 
+    def test_update_sets_relay_vlan(self):
+        self.become_admin()
+        fabric = factory.make_Fabric()
+        vlan = factory.make_VLAN(fabric=fabric)
+        uri = get_vlan_uri(vlan)
+        relay_vlan = factory.make_VLAN()
+        response = self.client.put(uri, {
+            "relay_vlan": relay_vlan.id,
+        })
+        self.assertEqual(
+            http.client.OK, response.status_code, response.content)
+        parsed_vlan = json.loads(
+            response.content.decode(settings.DEFAULT_CHARSET))
+        vlan = reload_object(vlan)
+        self.assertEqual(relay_vlan.vid, parsed_vlan['relay_vlan']['vid'])
+        self.assertEqual(relay_vlan, vlan.relay_vlan)
+
     def test_update_with_fabric(self):
         self.become_admin()
         fabric = factory.make_Fabric()
 
=== modified file 'src/maasserver/api/vlans.py'
--- src/maasserver/api/vlans.py	2016-04-27 20:40:24 +0000
+++ src/maasserver/api/vlans.py	2016-12-06 08:04:41 +0000
@@ -26,6 +26,7 @@
     'secondary_rack',
     'dhcp_on',
     'external_dhcp',
+    'relay_vlan',
 )
 
 
@@ -165,12 +166,18 @@
         :type vid: integer
         :param mtu: The MTU to use on the VLAN.
         :type mtu: integer
-        :Param dhcp_on: Whether or not DHCP should be managed on the VLAN.
+        :param dhcp_on: Whether or not DHCP should be managed on the VLAN.
         :type dhcp_on: boolean
         :param primary_rack: The primary rack controller managing the VLAN.
         :type primary_rack: system_id
         :param secondary_rack: The secondary rack controller manging the VLAN.
         :type secondary_rack: system_id
+        :param relay_vlan: Only set when this VLAN will be using a DHCP relay
+            to forward DHCP requests to another VLAN that MAAS is or will run
+            the DHCP server. MAAS will not run the DHCP relay itself, it must
+            be configured to proxy reqests to the primary and/or secondary
+            rack controller interfaces for the VLAN specified in this field.
+        :type relay_vlan: ID of VLAN
 
         Returns 404 if the fabric or VLAN is not found.
         """
 
=== modified file 'src/maasserver/dhcp.py'
--- src/maasserver/dhcp.py	2016-12-03 16:33:44 +0000
+++ src/maasserver/dhcp.py	2016-12-06 08:04:41 +0000
@@ -29,10 +29,7 @@
     IPRANGE_TYPE,
     SERVICE_STATUS,
 )
-from maasserver.exceptions import (
-    DHCPConfigurationError,
-    UnresolvableHost,
-)
+from maasserver.exceptions import UnresolvableHost
 from maasserver.models import (
     Config,
     DHCPSnippet,
@@ -194,18 +191,19 @@
         return []
 
 
-def get_managed_vlans_for(rack_controller):
-    """Return list of `VLAN` for the `rack_controller` when DHCP is enabled and
+def gen_managed_vlans_for(rack_controller):
+    """Yeilds each `VLAN` for the `rack_controller` when DHCP is enabled and
     `rack_controller` is either the `primary_rack` or the `secondary_rack`.
     """
     interfaces = rack_controller.interface_set.filter(
         Q(vlan__dhcp_on=True) & (
             Q(vlan__primary_rack=rack_controller) |
-            Q(vlan__secondary_rack=rack_controller))).select_related("vlan")
-    return {
-        interface.vlan
-        for interface in interfaces
-    }
+            Q(vlan__secondary_rack=rack_controller)))
+    interfaces = interfaces.prefetch_related("vlan__relay_vlans")
+    for interface in interfaces:
+        yield interface.vlan
+        for relayed_vlan in interface.vlan.relay_vlans.all():
+            yield relayed_vlan
 
 
 def ip_is_on_vlan(ip_address, vlan):
@@ -460,12 +458,6 @@
     interfaces = get_interfaces_with_ip_on_vlan(
         rack_controller, vlan, ip_version)
     interface = get_best_interface(interfaces)
-    if interface is None:
-        raise DHCPConfigurationError(
-            "No IPv%d interface on rack controller '%s' has an IP address on "
-            "any subnet on VLAN '%s.%d'." % (
-                ip_version, rack_controller.hostname, vlan.fabric.name,
-                vlan.vid))
 
     # Generate the failover peer for this VLAN.
     if vlan.secondary_rack_id is not None:
@@ -497,7 +489,7 @@
     hosts = make_hosts_for_subnets(subnets, nodes_dhcp_snippets)
     return (
         peer_config, sorted(subnet_configs, key=itemgetter("subnet")),
-        hosts, interface.name)
+        hosts, None if interface is None else interface.name)
 
 
 @synchronous
@@ -506,7 +498,7 @@
     """Return tuple with IPv4 and IPv6 configurations for the
     rack controller."""
     # Get list of all vlans that are being managed by the rack controller.
-    vlans = get_managed_vlans_for(rack_controller)
+    vlans = gen_managed_vlans_for(rack_controller)
 
     # Group the subnets on each VLAN into IPv4 and IPv6 subnets.
     vlan_subnets = {
@@ -562,52 +554,40 @@
     for vlan, (subnets_v4, subnets_v6) in vlan_subnets.items():
         # IPv4
         if len(subnets_v4) > 0:
-            try:
-                config = get_dhcp_configure_for(
-                    4, rack_controller, vlan, subnets_v4, ntp_servers,
-                    default_domain, dhcp_snippets)
-            except DHCPConfigurationError:
-                # XXX bug #1602412: this silently breaks DHCPv4, but we cannot
-                # allow it to crash here since DHCPv6 might be able to run.
-                # This error may be irrelevant if there is an IPv4 network in
-                # the MAAS model which is not configured on the rack, and the
-                # user only wants to serve DHCPv6. But it is still something
-                # worth noting, so log it and continue.
-                log.err(None, "Failure configuring DHCPv4.")
-            else:
-                failover_peer, subnets, hosts, interface = config
-                if failover_peer is not None:
-                    failover_peers_v4.append(failover_peer)
-                shared_networks_v4.append({
-                    "name": "vlan-%d" % vlan.id,
-                    "subnets": subnets,
-                })
-                hosts_v4.extend(hosts)
+            config = get_dhcp_configure_for(
+                4, rack_controller, vlan, subnets_v4, ntp_servers,
+                default_domain, dhcp_snippets)
+            failover_peer, subnets, hosts, interface = config
+            if failover_peer is not None:
+                failover_peers_v4.append(failover_peer)
+            shared_networks_v4.append({
+                "name": "vlan-%d" % vlan.id,
+                "subnets": subnets,
+            })
+            hosts_v4.extend(hosts)
+            if interface is not None:
                 interfaces_v4.add(interface)
         # IPv6
         if len(subnets_v6) > 0:
-            try:
-                config = get_dhcp_configure_for(
-                    6, rack_controller, vlan, subnets_v6,
-                    ntp_servers, default_domain, dhcp_snippets)
-            except DHCPConfigurationError:
-                # XXX bug #1602412: this silently breaks DHCPv6, but we cannot
-                # allow it to crash here since DHCPv4 might be able to run.
-                # This error may be irrelevant if there is an IPv6 network in
-                # the MAAS model which is not configured on the rack, and the
-                # user only wants to serve DHCPv4. But it is still something
-                # worth noting, so log it and continue.
-                log.err(None, "Failure configuring DHCPv6.")
-            else:
-                failover_peer, subnets, hosts, interface = config
-                if failover_peer is not None:
-                    failover_peers_v6.append(failover_peer)
-                shared_networks_v6.append({
-                    "name": "vlan-%d" % vlan.id,
-                    "subnets": subnets,
-                })
-                hosts_v6.extend(hosts)
+            config = get_dhcp_configure_for(
+                6, rack_controller, vlan, subnets_v6,
+                ntp_servers, default_domain, dhcp_snippets)
+            failover_peer, subnets, hosts, interface = config
+            if failover_peer is not None:
+                failover_peers_v6.append(failover_peer)
+            shared_networks_v6.append({
+                "name": "vlan-%d" % vlan.id,
+                "subnets": subnets,
+            })
+            hosts_v6.extend(hosts)
+            if interface is not None:
                 interfaces_v6.add(interface)
+    # When no interfaces exist for each IP version clear the shared networks
+    # as DHCP server cannot be started and needs to be stopped.
+    if len(interfaces_v4) == 0:
+        shared_networks_v4 = {}
+    if len(interfaces_v6) == 0:
+        shared_networks_v6 = {}
     return DHCPConfigurationForRack(
         failover_peers_v4, shared_networks_v4, hosts_v4, interfaces_v4,
         failover_peers_v6, shared_networks_v6, hosts_v6, interfaces_v6,
 
=== modified file 'src/maasserver/exceptions.py'
--- src/maasserver/exceptions.py	2016-03-28 13:54:47 +0000
+++ src/maasserver/exceptions.py	2016-12-06 08:04:41 +0000
@@ -199,7 +199,3 @@
     information.
     """
     api_error = int(http.client.SERVICE_UNAVAILABLE)
-
-
-class DHCPConfigurationError(MAASException):
-    """Raised when the configuration of DHCP hits a problem."""
 
=== modified file 'src/maasserver/forms_vlan.py'
--- src/maasserver/forms_vlan.py	2016-04-27 20:38:06 +0000
+++ src/maasserver/forms_vlan.py	2016-12-06 08:04:41 +0000
@@ -31,6 +31,7 @@
             'dhcp_on',
             'primary_rack',
             'secondary_rack',
+            'relay_vlan',
             )
 
     def __init__(self, *args, **kwargs):
@@ -40,6 +41,7 @@
         if instance is None and self.fabric is None:
             raise ValueError("Form requires either a instance or a fabric.")
         self._set_up_rack_fields()
+        self._set_up_relay_vlan()
 
     def _set_up_rack_fields(self):
         qs = RackController.objects.filter_by_vids([self.instance.vid])
@@ -61,6 +63,22 @@
             secondary_rack = RackController.objects.get(id=secondary_rack_id)
             self.initial['secondary_rack'] = secondary_rack.system_id
 
+    def _set_up_relay_vlan(self):
+        # Configure the relay_vlan fields to include only VLAN's that are
+        # not already on a relay_vlan. If this is an update then it cannot
+        # be itself or never set when dhcp_on is True.
+        possible_relay_vlans = VLAN.objects.filter(relay_vlan__isnull=True)
+        if self.instance is not None:
+            possible_relay_vlans = possible_relay_vlans.exclude(
+                id=self.instance.id)
+            if self.instance.dhcp_on:
+                possible_relay_vlans = VLAN.objects.none()
+                if self.instance.relay_vlan is not None:
+                    possible_relay_vlans = VLAN.objects.filter(
+                        id=self.instance.relay_vlan.id)
+        self.fields['relay_vlan'] = forms.ModelChoiceField(
+            queryset=possible_relay_vlans, required=False)
+
     def clean(self):
         cleaned_data = super(VLANForm, self).clean()
         # Automatically promote the secondary rack controller to the primary
@@ -120,5 +138,12 @@
         interface = super(VLANForm, self).save(commit=False)
         if self.fabric is not None:
             interface.fabric = self.fabric
+        if ('relay_vlan' in self.data and
+                not self.cleaned_data.get('relay_vlan')):
+            # relay_vlan is being cleared.
+            interface.relay_vlan = None
+        if interface.dhcp_on:
+            # relay_vlan cannot be set when dhcp is on.
+            interface.relay_vlan = None
         interface.save()
         return interface
 
=== modified file 'src/maasserver/migrations/builtin/maasserver/0056_add_description_to_fabric_and_space.py'
--- src/maasserver/migrations/builtin/maasserver/0056_add_description_to_fabric_and_space.py	2016-07-30 01:17:54 +0000
+++ src/maasserver/migrations/builtin/maasserver/0056_add_description_to_fabric_and_space.py	2016-12-06 08:04:41 +0000
@@ -44,6 +44,6 @@
         migrations.AlterField(
             model_name='subnet',
             name='vlan',
-            field=models.ForeignKey(to='maasserver.VLAN', default=maasserver.models.subnet.get_default_vlan, on_delete=django.db.models.deletion.PROTECT),
+            field=models.ForeignKey(to='maasserver.VLAN', default=None, on_delete=django.db.models.deletion.PROTECT),
         ),
     ]
 
=== added file 'src/maasserver/migrations/builtin/maasserver/0095_vlan_relay_vlan.py'
--- src/maasserver/migrations/builtin/maasserver/0095_vlan_relay_vlan.py	1970-01-01 00:00:00 +0000
+++ src/maasserver/migrations/builtin/maasserver/0095_vlan_relay_vlan.py	2016-12-06 08:04:41 +0000
@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import (
+    migrations,
+    models,
+)
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('maasserver', '0094_add_unmanaged_subnets'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='vlan',
+            name='relay_vlan',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.SET_NULL, null=True, blank=True, related_name='relay_vlans', to='maasserver.VLAN'),
+        ),
+    ]
 
=== added file 'src/maasserver/migrations/builtin/maasserver/0096_set_default_vlan_field.py'
--- src/maasserver/migrations/builtin/maasserver/0096_set_default_vlan_field.py	1970-01-01 00:00:00 +0000
+++ src/maasserver/migrations/builtin/maasserver/0096_set_default_vlan_field.py	2016-12-06 08:04:41 +0000
@@ -0,0 +1,24 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import (
+    migrations,
+    models,
+)
+import django.db.models.deletion
+import maasserver.models.subnet
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('maasserver', '0095_vlan_relay_vlan'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='subnet',
+            name='vlan',
+            field=models.ForeignKey(to='maasserver.VLAN', default=maasserver.models.subnet.get_default_vlan, on_delete=django.db.models.deletion.PROTECT),
+        ),
+    ]
 
=== modified file 'src/maasserver/models/tests/test_vlan.py'
--- src/maasserver/models/tests/test_vlan.py	2016-10-19 18:06:01 +0000
+++ src/maasserver/models/tests/test_vlan.py	2016-12-06 08:04:41 +0000
@@ -88,6 +88,14 @@
 
 class TestVLAN(MAASServerTestCase):
 
+    def test_delete_relay_vlan_doesnt_delete_vlan(self):
+        relay_vlan = factory.make_VLAN()
+        vlan = factory.make_VLAN(relay_vlan=relay_vlan)
+        relay_vlan.delete()
+        vlan = reload_object(vlan)
+        self.assertIsNotNone(vlan)
+        self.assertIsNone(vlan.relay_vlan)
+
     def test_get_name_for_default_vlan_is_untagged(self):
         fabric = factory.make_Fabric()
         self.assertEqual("untagged", fabric.get_default_vlan().get_name())
 
=== modified file 'src/maasserver/models/vlan.py'
--- src/maasserver/models/vlan.py	2016-10-20 19:39:48 +0000
+++ src/maasserver/models/vlan.py	2016-12-06 08:04:41 +0000
@@ -14,6 +14,7 @@
 from django.db.models import (
     BooleanField,
     CharField,
+    deletion,
     ForeignKey,
     IntegerField,
     Manager,
@@ -169,6 +170,10 @@
         'RackController', null=True, blank=True, editable=True,
         related_name='+')
 
+    relay_vlan = ForeignKey(
+        'self', null=True, blank=True, editable=True,
+        related_name='relay_vlans', on_delete=deletion.SET_NULL)
+
     def __str__(self):
         return "%s.%s" % (self.fabric.get_name(), self.get_name())
 
 
=== modified file 'src/maasserver/static/js/angular/controllers/tests/test_vlan_details.js'
--- src/maasserver/static/js/angular/controllers/tests/test_vlan_details.js	2016-10-19 18:06:01 +0000
+++ src/maasserver/static/js/angular/controllers/tests/test_vlan_details.js	2016-12-06 08:04:41 +0000
@@ -427,6 +427,42 @@
         expect(controller.actionError).toBe(null);
     });
 
+    it("performAction for relay_dhcp called with all params", function() {
+        var controller = makeControllerResolveSetActiveItem();
+        controller.actionOption = controller.RELAY_DHCP_ACTION;
+        // This will populate the default values for the racks with
+        // the current values from the mock objects.
+        controller.actionOptionChanged();
+        controller.provideDHCPAction.subnet = 1;
+        controller.provideDHCPAction.gatewayIP = "192.168.0.1";
+        controller.provideDHCPAction.startIP = "192.168.0.2";
+        controller.provideDHCPAction.endIP = "192.168.0.254";
+        var relay = {
+            id: makeInteger(5001, 6000)
+        };
+        VLANsManager._items = [relay];
+        controller.provideDHCPAction.relayVLAN = relay;
+        var defer = $q.defer();
+        spyOn(VLANsManager, "configureDHCP").and.returnValue(
+            defer.promise);
+        controller.actionGo();
+        defer.resolve();
+        $scope.$digest();
+        expect(VLANsManager.configureDHCP).toHaveBeenCalledWith(
+            controller.vlan,
+            [],
+            {
+                subnet: 1,
+                gateway: "192.168.0.1",
+                start: "192.168.0.2",
+                end: "192.168.0.254"
+            },
+            relay.id
+        );
+        expect(controller.actionOption).toBe(null);
+        expect(controller.actionError).toBe(null);
+    });
+
     it("performAction for disable_dhcp called with all params", function() {
         var controller = makeControllerResolveSetActiveItem();
         controller.actionOption = controller.DISABLE_DHCP_ACTION;
@@ -457,6 +493,7 @@
         controller.actionOptionChanged();
         expect(controller.provideDHCPAction).toEqual({
             subnet: subnet.id,
+            relayVLAN: null,
             primaryRack: "p1",
             secondaryRack: "p2",
             maxIPs: 0,
@@ -488,6 +525,7 @@
         controller.actionOptionChanged();
         expect(controller.provideDHCPAction).toEqual({
             subnet: subnet.id,
+            relayVLAN: null,
             primaryRack: "p1",
             secondaryRack: "p2",
             maxIPs: 26,
@@ -551,30 +589,45 @@
             expect(controller.actionOptions).toEqual([]);
         });
 
-        it("returns enable_dhcp and delete when dhcp is off",
+        it("returns enable_dhcp, relay_dhcp and delete when dhcp is off",
         function() {
             vlan.dhcp_on = false;
             UsersManager._authUser = {is_superuser: true};
             var controller = makeControllerResolveSetActiveItem();
             expect(controller.actionOptions).toEqual([
                 controller.PROVIDE_DHCP_ACTION,
+                controller.RELAY_DHCP_ACTION,
                 controller.DELETE_ACTION
             ]);
             expect(controller.PROVIDE_DHCP_ACTION.title).toBe("Provide DHCP");
         });
 
-        it("returns disable_dhcp, enable_dhcp (with new title) and delete "+
+        it("returns enable_dhcp (with new title), disable_dhcp and delete "+
             "when dhcp is on", function() {
             vlan.dhcp_on = true;
             UsersManager._authUser = {is_superuser: true};
             var controller = makeControllerResolveSetActiveItem();
             expect(controller.actionOptions).toEqual([
+                controller.PROVIDE_DHCP_ACTION,
                 controller.DISABLE_DHCP_ACTION,
-                controller.PROVIDE_DHCP_ACTION,
                 controller.DELETE_ACTION
             ]);
             expect(controller.PROVIDE_DHCP_ACTION.title).toBe(
                 "Reconfigure DHCP");
         });
+
+        it("returns relay_dhcp (with new title), disable_dhcp and delete "+
+            "when relay_vlan is set", function() {
+            vlan.relay_vlan = 5001;
+            UsersManager._authUser = {is_superuser: true};
+            var controller = makeControllerResolveSetActiveItem();
+            expect(controller.actionOptions).toEqual([
+                controller.RELAY_DHCP_ACTION,
+                controller.DISABLE_DHCP_ACTION,
+                controller.DELETE_ACTION
+            ]);
+            expect(controller.RELAY_DHCP_ACTION.title).toBe(
+                "Reconfigure DHCP relay");
+        });
     });
 });
 
=== modified file 'src/maasserver/static/js/angular/controllers/vlan_details.js'
--- src/maasserver/static/js/angular/controllers/vlan_details.js	2016-10-19 18:06:01 +0000
+++ src/maasserver/static/js/angular/controllers/vlan_details.js	2016-12-06 08:04:41 +0000
@@ -4,6 +4,18 @@
  * MAAS VLAN Details Controller
  */
 
+angular.module('MAAS').filter('ignoreSelf', function () {
+    return function(objects, self) {
+        var filtered = [];
+        angular.forEach(objects, function(obj) {
+            if(obj !== self) {
+                filtered.push(obj);
+            }
+        });
+        return filtered;
+    };
+});
+
 angular.module('MAAS').controller('VLANDetailsController', [
     '$scope', '$rootScope', '$routeParams', '$filter', '$location',
     'VLANsManager', 'SubnetsManager', 'SpacesManager', 'FabricsManager',
@@ -27,10 +39,15 @@
         $rootScope.page = "networks";
 
         vm.PROVIDE_DHCP_ACTION = {
-            // Note: 'title' is setubndynamically depending on whether or not
+            // Note: 'title' is set dynamically depending on whether or not
             // DHCP is already enabled on this VLAN.
             name: "enable_dhcp"
         };
+        vm.RELAY_DHCP_ACTION = {
+            // Note: 'title' is set ndynamically depending on whether or not
+            // DHCP relay is already enabled on this VLAN.
+            name: "relay_dhcp"
+        };
         vm.DISABLE_DHCP_ACTION = {
             name: "disable_dhcp",
             title: "Disable DHCP"
@@ -47,6 +64,7 @@
         vm.actionOption = null;
         vm.actionOptions = [];
         vm.vlanManager = VLANsManager;
+        vm.vlans = VLANsManager.getItems();
         vm.subnets = SubnetsManager.getItems();
         vm.spaces = SpacesManager.getItems();
         vm.fabrics = FabricsManager.getItems();
@@ -78,10 +96,15 @@
         // Initialize the provideDHCPAction structure with the current primary
         // and secondary rack, plus an indication regarding whether or not
         // adding a dynamic IP range is required.
-        vm.initProvideDHCP = function() {
+        vm.initProvideDHCP = function(forRelay) {
             vm.provideDHCPAction = {};
             var dhcp = vm.provideDHCPAction;
             dhcp.subnet = null;
+            dhcp.relayVLAN = null;
+            if (angular.isNumber(vm.vlan.relay_vlan)) {
+                dhcp.relayVLAN = VLANsManager.getItemFromList(
+                    vm.vlan.relay_vlan);
+            }
             if (angular.isObject(vm.primaryRack)) {
                 dhcp.primaryRack = vm.primaryRack.system_id;
             } else if(vm.relatedControllers.length > 0) {
@@ -140,15 +163,19 @@
             }
             // Since we are setting default values for these three options,
             // ensure all the appropriate updates occur.
-            vm.updatePrimaryRack();
-            vm.updateSecondaryRack();
-            vm.updateSubnet();
+            if(!forRelay) {
+                vm.updatePrimaryRack();
+                vm.updateSecondaryRack();
+            }
+            vm.updateSubnet(forRelay);
         };
 
         // Called when the actionOption has changed.
         vm.actionOptionChanged = function() {
             if(vm.actionOption.name === "enable_dhcp") {
-                vm.initProvideDHCP();
+                vm.initProvideDHCP(false);
+            } else if(vm.actionOption.name === "relay_dhcp") {
+                vm.initProvideDHCP(true);
             }
             // Clear the action error.
             vm.actionError = null;
@@ -200,7 +227,7 @@
         };
 
         // Called from the Provide DHCP form when the subnet selection changes.
-        vm.updateSubnet = function() {
+        vm.updateSubnet = function(forRelay) {
             var dhcp = vm.provideDHCPAction;
             var subnet = SubnetsManager.getItemFromList(dhcp.subnet);
             if(angular.isObject(subnet)) {
@@ -212,10 +239,17 @@
                 }
                 if(angular.isObject(iprange) && iprange.num_addresses > 0) {
                     dhcp.maxIPs = iprange.num_addresses;
-                    dhcp.startIP = iprange.start;
-                    dhcp.endIP = iprange.end;
-                    dhcp.startPlaceholder = iprange.start;
-                    dhcp.endPlaceholder = iprange.end;
+                    if(forRelay) {
+                        dhcp.startIP = "";
+                        dhcp.endIP = "";
+                        dhcp.startPlaceholder = iprange.start + "( optional)";
+                        dhcp.endPlaceholder = iprange.end + " (optional)";
+                    } else {
+                        dhcp.startIP = iprange.start;
+                        dhcp.endIP = iprange.end;
+                        dhcp.startPlaceholder = iprange.start;
+                        dhcp.endPlaceholder = iprange.end;
+                    }
                 } else {
                     // Need to add a dynamic range, but according to our data,
                     // there is no room on the subnet for a dynamic range.
@@ -226,8 +260,14 @@
                     dhcp.endPlaceholder = "(no available IPs)";
                 }
                 if(angular.isString(suggested_gateway)) {
-                    dhcp.gatewayIP = suggested_gateway;
-                    dhcp.gatewayPlaceholder = suggested_gateway;
+                    if(forRelay) {
+                      dhcp.gatewayIP = "";
+                      dhcp.gatewayPlaceholder = (
+                          suggested_gateway + " (optional)");
+                    } else {
+                        dhcp.gatewayIP = suggested_gateway;
+                        dhcp.gatewayPlaceholder = suggested_gateway;
+                    }
                 } else {
                     // This means the subnet already has a gateway, so don't
                     // bother populating it.
@@ -261,8 +301,24 @@
             vm.actionError = null;
         };
 
+        // Return True if the current action can be performed.
+        vm.canPerformAction = function() {
+            if(vm.actionOption.name === "enable_dhcp") {
+                return vm.relatedSubnets.length > 0;
+            } else if(vm.actionOption.name === "relay_dhcp") {
+                return angular.isObject(vm.provideDHCPAction.relayVLAN);
+            } else {
+                return true;
+            }
+        };
+
         // Perform the action.
         vm.actionGo = function() {
+            // Do nothing if action cannot be performed.
+            if(!vm.canPerformAction()) {
+               return;
+            }
+
             if(vm.actionOption.name === "enable_dhcp") {
                 var dhcp = vm.provideDHCPAction;
                 var controllers = [];
@@ -294,6 +350,23 @@
                         vm.actionError = result.error;
                         vm.actionOption = vm.PROVIDE_DHCP_ACTION;
                     });
+            } else if(vm.actionOption.name === "relay_dhcp") {
+                // These will be undefined if they don't exist, and the region
+                // will simply get an empty dictionary.
+                var extraDHCP = {};
+                extraDHCP.subnet = vm.provideDHCPAction.subnet;
+                extraDHCP.start = vm.provideDHCPAction.startIP;
+                extraDHCP.end = vm.provideDHCPAction.endIP;
+                extraDHCP.gateway = vm.provideDHCPAction.gatewayIP;
+                var relay = vm.provideDHCPAction.relayVLAN.id;
+                VLANsManager.configureDHCP(
+                    vm.vlan, [], extraDHCP, relay).then(function() {
+                        vm.actionOption = null;
+                        vm.actionError = null;
+                    }, function(result) {
+                        vm.actionError = result.error;
+                        vm.actionOption = vm.RELAY_DHCP_ACTION;
+                    });
             } else if(vm.actionOption.name === "disable_dhcp") {
                 VLANsManager.disableDHCP(vm.vlan).then(function() {
                     vm.actionOption = null;
@@ -319,6 +392,30 @@
             return vm.actionError !== null;
         };
 
+        // Return the name of the VLAN.
+        vm.getFullVLANName = function(vlan_id) {
+            var vlan = VLANsManager.getItemFromList(vlan_id);
+            var fabric = FabricsManager.getItemFromList(vlan.fabric);
+            return (
+                FabricsManager.getName(fabric) + "." +
+                VLANsManager.getName(vlan));
+        };
+
+        // Return the current DHCP status.
+        vm.getDHCPStatus = function() {
+            if(vm.vlan) {
+              if(vm.vlan.dhcp_on) {
+                return "Enabled";
+              } else if(vm.vlan.relay_vlan) {
+                return "Relayed via " + vm.getFullVLANName(vm.vlan.relay_vlan);
+              } else {
+                return "Disabled";
+              }
+            } else {
+              return "";
+            }
+        };
+
         // Updates the page title.
         function updateTitle() {
             var vlan = vm.vlan;
@@ -413,13 +510,22 @@
             // object, since it's watched from $scope.)
             vm.actionOptions.length = 0;
             if(UsersManager.isSuperUser()) {
-                if(vlan.dhcp_on === true) {
-                    vm.actionOptions.push(vm.DISABLE_DHCP_ACTION);
-                    vm.PROVIDE_DHCP_ACTION.title = "Reconfigure DHCP";
+                if(!vlan.relay_vlan) {
+                  if(vlan.dhcp_on === true) {
+                      vm.PROVIDE_DHCP_ACTION.title = "Reconfigure DHCP";
+                      vm.actionOptions.push(vm.PROVIDE_DHCP_ACTION);
+                      vm.actionOptions.push(vm.DISABLE_DHCP_ACTION);
+                  } else {
+                      vm.PROVIDE_DHCP_ACTION.title = "Provide DHCP";
+                      vm.RELAY_DHCP_ACTION.title = "Relay DHCP";
+                      vm.actionOptions.push(vm.PROVIDE_DHCP_ACTION);
+                      vm.actionOptions.push(vm.RELAY_DHCP_ACTION);
+                  }
                 } else {
-                    vm.PROVIDE_DHCP_ACTION.title = "Provide DHCP";
+                  vm.actionOptions.push(vm.RELAY_DHCP_ACTION);
+                  vm.actionOptions.push(vm.DISABLE_DHCP_ACTION);
+                  vm.RELAY_DHCP_ACTION.title = "Reconfigure DHCP relay";
                 }
-                vm.actionOptions.push(vm.PROVIDE_DHCP_ACTION);
                 if(!vm.isFabricDefault) {
                     vm.actionOptions.push(vm.DELETE_ACTION);
                 }
@@ -467,6 +573,8 @@
             $scope.$watch("vlanDetails.vlan.name", updateTitle);
             $scope.$watch("vlanDetails.vlan.vid", updateTitle);
             $scope.$watch("vlanDetails.vlan.dhcp_on", updatePossibleActions);
+            $scope.$watch(
+                "vlanDetails.vlan.relay_vlan", updatePossibleActions);
             $scope.$watch("vlanDetails.fabric.name", updateTitle);
             $scope.$watch(
                 "vlanDetails.vlan.primary_rack", updateManagementRacks);
 
=== modified file 'src/maasserver/static/js/angular/factories/tests/test_vlans.js'
--- src/maasserver/static/js/angular/factories/tests/test_vlans.js	2016-05-11 19:01:48 +0000
+++ src/maasserver/static/js/angular/factories/tests/test_vlans.js	2016-12-06 08:04:41 +0000
@@ -38,14 +38,16 @@
             var result = {};
             var controllers = ["a", "b"];
             var extra = {"c": "d"};
+            var relay = makeInteger(1, 500);
             spyOn(RegionConnection, "callMethod").and.returnValue(result);
             expect(VLANsManager.configureDHCP(
-                obj, controllers, extra)).toBe(result);
+                obj, controllers, extra, relay)).toBe(result);
             expect(RegionConnection.callMethod).toHaveBeenCalledWith(
                 "vlan.configure_dhcp", {
                     id: obj.id,
                     controllers: controllers,
-                    extra: extra
+                    extra: extra,
+                    relay_vlan: relay
                 }, true);
         });
     });
@@ -60,7 +62,8 @@
             expect(RegionConnection.callMethod).toHaveBeenCalledWith(
                 "vlan.configure_dhcp", {
                     id: obj.id,
-                    controllers: []
+                    controllers: [],
+                    relay_vlan: null
                 }, true);
         });
     });
 
=== modified file 'src/maasserver/static/js/angular/factories/vlans.js'
--- src/maasserver/static/js/angular/factories/vlans.js	2016-05-11 19:01:48 +0000
+++ src/maasserver/static/js/angular/factories/vlans.js	2016-12-06 08:04:41 +0000
@@ -53,13 +53,17 @@
 
         // Configure DHCP on the VLAN
         VLANsManager.prototype.configureDHCP = function(
-           vlan, controllers, extra) {
+           vlan, controllers, extra, relay_vlan) {
+           var params = {
+               "id": vlan.id,
+               "controllers": controllers,
+               "extra": extra
+           };
+           if(relay_vlan === null || angular.isNumber(relay_vlan)) {
+              params.relay_vlan = relay_vlan;
+           }
            return RegionConnection.callMethod(
-                "vlan.configure_dhcp", {
-                    "id": vlan.id,
-                    "controllers": controllers,
-                    "extra": extra
-                }, true);
+                "vlan.configure_dhcp", params, true);
         };
 
         // Disable DHCP on the VLAN
@@ -67,7 +71,8 @@
             return RegionConnection.callMethod(
                 "vlan.configure_dhcp", {
                     "id": vlan.id,
-                    "controllers": []
+                    "controllers": [],
+                    "relay_vlan": null
                 }, true);
         };
 
 
=== modified file 'src/maasserver/static/partials/vlan-details.html'
--- src/maasserver/static/partials/vlan-details.html	2016-11-17 11:46:08 +0000
+++ src/maasserver/static/partials/vlan-details.html	2016-12-06 08:04:41 +0000
@@ -1,27 +1,27 @@
-<div data-ng-hide="vlanDetails.loaded">
+<div data-ng-if="!vlanDetails.loaded">
     <header class="page-header" sticky>
         <div class="wrapper--inner">
             <h1 class="page-header__title">Loading...</h1>
         </div>
     </header>
 </div>
-<div class="ng-hide" data-ng-show="vlanDetails.loaded">
+<div data-ng-if="vlanDetails.loaded">
     <header class="page-header" sticky>
         <div class="wrapper--inner">
             <h1 class="page-header__title">{$ vlanDetails.title $}</h1>
             <!-- "Take action" dropdown -->
-            <div class="page-header__controls" data-ng-show="vlanDetails.actionOptions.length">
+            <div class="page-header__controls" data-ng-if="vlanDetails.actionOptions.length">
                 <div data-maas-cta="vlanDetails.actionOptions"
                     data-ng-model="vlanDetails.actionOption"
                     data-ng-change="vlanDetails.actionOptionChanged()">
                 </div>
             </div>
-            <div class="page-header__dropdown" data-ng-class="{ 'is-open': vlanDetails.actionOption }">
-                <section class="page-header__section twelve-col u-margin--bottom-none ng-hide" data-ng-show="vlanDetails.actionOption.name === 'enable_dhcp'">
-                    <h3 class="page-header__dropdown-title" data-ng-show="vlanDetails.actionOption.name === 'enable_dhcp'">Provide DHCP</h3>
+            <div class="page-header__dropdown" data-ng-class="{ 'is-open': vlanDetails.actionOption }" data-ng-if="vlanDetails.actionOption">
+                <section class="page-header__section twelve-col u-margin--bottom-none" data-ng-if="vlanDetails.actionOption.name === 'enable_dhcp'">
+                    <h3 class="page-header__dropdown-title">Provide DHCP</h3>
                     <form class="form form--stack">
                         <!-- This is just for visual reasons, since we need an additional border to begin the form if there is no error. -->
-                        <fieldset class="form__fieldset six-col" data-ng-show="vlanDetails.actionOption.name === 'enable_dhcp'">
+                        <fieldset class="form__fieldset six-col">
                             <div class="form__group" data-ng-hide="vlanDetails.relatedSubnets.length === 0">
                                 <label for="primary-rack" class="form__group-label two-col">{$ vlanDetails.relatedControllers.length <= 1 ? "Rack controller" : "Primary controller" $}</label>
                                 <div class="form__group-input three-col">
@@ -32,7 +32,7 @@
                                         <option value=""
                                                 disabled="disabled"
                                                 selected="selected"
-                                                data-ng-show="vlanDetails.provideDHCPAction.primaryRack === ''">Choose primary controller</option>
+                                                data-ng-if="vlanDetails.provideDHCPAction.primaryRack === ''">Choose primary controller</option>
                                     </select>
                                 </div>
                             </div>
@@ -40,14 +40,14 @@
                                 <label for="secondary-rack" class="form__group-label two-col">Secondary controller</label>
                                 <div class="form__group-input three-col">
                                     <select name="secondary-rack"
-                                            data-ng-show="vlanDetails.relatedControllers.length > 1"
+                                            data-ng-if="vlanDetails.relatedControllers.length > 1"
                                             data-ng-disabled="!vlanDetails.provideDHCPAction.primaryRack && vlanDetails.relatedControllers.length > 1"
                                             data-ng-model="vlanDetails.provideDHCPAction.secondaryRack"
                                             data-ng-change="vlanDetails.updateSecondaryRack()"
                                             data-ng-options="rack.system_id as rack.hostname for rack in vlanDetails.relatedControllers | filter:vlanDetails.filterPrimaryRack">
                                         <option value=""
                                                 selected="selected"
-                                                data-ng-show="vlanDetails.relatedControllers.length >= 2"></option>
+                                                data-ng-if="vlanDetails.relatedControllers.length >= 2"></option>
                                     </select>
                                 </div>
                             </div>
@@ -57,7 +57,7 @@
                                 <div class="form__group-input three-col">
                                     <select name="subnet"
                                             data-ng-model="vlanDetails.provideDHCPAction.subnet"
-                                            data-ng-change="vlanDetails.updateSubnet()"
+                                            data-ng-change="vlanDetails.updateSubnet(false)"
                                             data-ng-options="row.subnet.id as row.subnet.cidr for row in vlanDetails.relatedSubnets">
                                         <option value="" disabled="disabled" selected="selected">Choose subnet</option>
                                         <option value="" data-ng-if=""></option>
@@ -65,7 +65,7 @@
                                 </div>
                            </div>
                         </fieldset>
-                        <fieldset class="form__fieldset six-col last-col" data-ng-show="vlanDetails.actionOption.name === 'enable_dhcp'">
+                        <fieldset class="form__fieldset six-col last-col" data-ng-if="vlanDetails.actionOption.name === 'enable_dhcp'">
                             <div class="form__group"
                                  data-ng-hide="vlanDetails.provideDHCPAction.needsDynamicRange === false || vlanDetails.relatedSubnets.length === 0">
                                 <label for="start-ip" class="form__group-label two-col">Dynamic range start IP</label>
@@ -114,26 +114,101 @@
                         </fieldset>
                     </form>
                 </section>
-                <section class="page-header__section twelve-col u-margin--bottom-none" data-ng-hide="vlanDetails.isActionError()">
+                <section class="page-header__section twelve-col u-margin--bottom-none" data-ng-if="vlanDetails.actionOption.name === 'relay_dhcp'">
+                    <h3 class="page-header__dropdown-title">Relay DHCP</h3>
+                    <form class="form form--stack">
+                        <!-- This is just for visual reasons, since we need an additional border to begin the form if there is no error. -->
+                        <fieldset class="form__fieldset six-col">
+                            <div class="form__group">
+                                <label for="relay_vlan" class="form__group-label two-col">Relay VLAN</label>
+                                <div class="form__group-input three-col">
+                                    <select name="relay_vlan"
+                                            data-ng-model="vlanDetails.provideDHCPAction.relayVLAN"
+                                            data-ng-options="vlan as vlanDetails.getFullVLANName(vlan.id) for vlan in vlanDetails.vlans | ignoreSelf:vlanDetails.vlan">
+                                        <option value="" disabled="disabled" selected="selected">Choose relay VLAN</option>
+                                    </select>
+                                </div>
+                            </div>
+                            <div class="form__group"
+                                 data-ng-hide="vlanDetails.relatedSubnets.length === 0 || (vlanDetails.provideDHCPAction.needsDynamicRange === false && vlanDetails.provideDHCPAction.needsGatewayIP === false)">
+                                <label for="subnet" class="form__group-label two-col">Subnet</label>
+                                <div class="form__group-input three-col">
+                                    <select name="subnet"
+                                            data-ng-model="vlanDetails.provideDHCPAction.subnet"
+                                            data-ng-change="vlanDetails.updateSubnet(true)"
+                                            data-ng-options="row.subnet.id as row.subnet.cidr for row in vlanDetails.relatedSubnets">
+                                        <option value="" disabled="disabled" selected="selected">Choose subnet</option>
+                                        <option value="" data-ng-if=""></option>
+                                    </select>
+                                </div>
+                           </div>
+                        </fieldset>
+                        <fieldset class="form__fieldset six-col last-col">
+                            <div class="form__group"
+                                 data-ng-hide="vlanDetails.provideDHCPAction.needsDynamicRange === false || vlanDetails.relatedSubnets.length === 0">
+                                <label for="start-ip" class="form__group-label two-col">Dynamic range start IP</label>
+                                <div class="form__group-input three-col">
+                                    <input type="text"
+                                           name="start-ip"
+                                           size="39"
+                                           data-ng-placeholder="vlanDetails.provideDHCPAction.startPlaceholder"
+                                           data-ng-model="vlanDetails.provideDHCPAction.startIP"
+                                           data-ng-disabled="!vlanDetails.provideDHCPAction.subnet"
+                                           data-ng-change="vlanDetails.updateStartIP()">
+                                </div>
+                            </div>
+                            <div class="form__group" data-ng-hide="vlanDetails.provideDHCPAction.needsDynamicRange === false || vlanDetails.relatedSubnets.length === 0">
+                                <label for="end-ip" class="form__group-label two-col">Dynamic range end IP</label>
+                                <div class="form__group-input three-col">
+                                    <input type="text"
+                                           name="end-ip"
+                                           size="39"
+                                           data-ng-placeholder="vlanDetails.provideDHCPAction.endPlaceholder"
+                                           data-ng-model="vlanDetails.provideDHCPAction.endIP"
+                                           data-ng-disabled="!vlanDetails.provideDHCPAction.subnet"
+                                           data-ng-change="vlanDetails.updateEndIP()">
+                                </div>
+                            </div>
+                            <div class="form__group"
+                                 data-ng-hide="vlanDetails.provideDHCPAction.needsGatewayIP === false || vlanDetails.provideDHCPAction.subnetMissingGatewayIP === false || vlanDetails.relatedSubnets.length === 0">
+                                <label for="gateway-ip" class="form__group-label two-col">Gateway IP</label>
+                                <div class="form__group-input three-col">
+                                    <input type="text"
+                                           name="gateway-ip"
+                                           size="39"
+                                           data-ng-placeholder="vlanDetails.provideDHCPAction.gatewayPlaceholder"
+                                           data-ng-model="vlanDetails.provideDHCPAction.gatewayIP"
+                                           data-ng-disabled="!vlanDetails.provideDHCPAction.subnet"
+                                           data-ng-change="vlanDetails.updatendIP()">
+                                </div>
+                            </div>
+                        </fieldset>
+                    </form>
+                </section>
+                <section class="page-header__section twelve-col u-margin--bottom-none" data-ng-if="!vlanDetails.isActionError()">
                     <p class="page-header__message page-header__message--warning"
-                       data-ng-show="vlanDetails.actionOption.name === 'disable_dhcp'">
+                       data-ng-if="vlanDetails.actionOption.name === 'disable_dhcp' && vlanDetails.vlan.dhcp_on">
                         Are you sure you want to disable DHCP on this VLAN? All subnets on this VLAN will be affected.
                     </p>
+                    <p class="page-header__message page-header__message--warning"
+                       data-ng-if="vlanDetails.actionOption.name === 'disable_dhcp' && vlanDetails.vlan.relay_vlan">
+                        Are you sure you want to disable DHCP relay on this VLAN? All subnets on this VLAN will be affected.
+                    </p>
                     <p class="page-header__message page-header__message--error"
-                       data-ng-show="vlanDetails.actionOption.name === 'enable_dhcp' && vlanDetails.relatedSubnets.length === 0">
+                       data-ng-if="vlanDetails.actionOption.name === 'enable_dhcp' && vlanDetails.relatedSubnets.length === 0">
                         No subnets are available on this VLAN. DHCP cannot be enabled.
                     </p>
                     <p class="page-header__message page-header__message--warning"
-                       data-ng-show="vlanDetails.actionOption.name === 'delete'">
+                       data-ng-if="vlanDetails.actionOption.name === 'delete'">
                         Are you sure you want to delete this VLAN?
                     </p>
                     <div class="page-header__controls">
                         <a href="" class="button--base button--inline" data-ng-click="vlanDetails.actionCancel()">Cancel</a>
-                        <button class="button--primary button--inline" data-ng-click="vlanDetails.actionGo()" data-ng-disabled="vlanDetails.actionOption.name === 'enable_dhcp' && vlanDetails.relatedSubnets.length === 0">{$ vlanDetails.actionOption.title $}</button>
+                        <button class="button--primary button--inline" data-ng-click="vlanDetails.actionGo()" data-ng-disabled="!vlanDetails.canPerformAction()">{$ vlanDetails.actionOption.title $}</button>
                     </div>
                 </section>
-                <section class="page-header__section twelve-col u-margin--bottom-none ng-hide"
-                     data-ng-show="vlanDetails.isActionError()">
+                <section class="page-header__section twelve-col u-margin--bottom-none"
+                     data-ng-if="vlanDetails.isActionError()">
                     <p class="page-header__message page-header__message--error">{$ vlanDetails.actionError $}</p>
                     <div class="page-header__controls">
                         <a href="" class="button--base button--inline u-margin--right" data-ng-click="vlanDetails.actionCancel()">Cancel</a>
@@ -166,17 +241,17 @@
                         <dd class="four-col last-col">
                             <a href="#/fabric/{$ vlanDetails.fabric.id $}">{$ vlanDetails.fabric.name $}</a>
                         </dd>
-                        <dt class="two-col">DHCP</dt><dd class="four-col last-col">{$ vlanDetails.vlan.dhcp_on ? "Enabled" : "Disabled" $}</dd>
+                        <dt class="two-col">DHCP</dt><dd class="four-col last-col">{$ vlanDetails.getDHCPStatus() $}</dd>
                         <div data-ng-if="vlanDetails.vlan.external_dhcp">
                             <dt class="two-col">External DHCP</dt>
                             <dd class="four-col last-col">{$ vlanDetails.vlan.external_dhcp $}
                                 <i class="icon icon--warning tooltip" aria-label="Another DHCP server has been discovered on this VLAN. Enabling DHCP is not recommended."></i>
                             </dd>
                         </div>
-                        <div class="ng-hide" data-ng-show="vlanDetails.primaryRack">
+                        <div data-ng-if="vlanDetails.primaryRack">
                             <dt class="two-col">Primary controller <span class="icon icon--help tooltip" aria-label="The rack controller where DHCP service runs on."></span></dt><dd class="four-col last-col">{$ vlanDetails.primaryRack.hostname $}</dd>
                         </div>
-                        <div class="ng-hide" data-ng-show="vlanDetails.secondaryRack">
+                        <div data-ng-if="vlanDetails.secondaryRack">
                             <dt class="two-col">Secondary controller <span class="icon icon--help tooltip" aria-label="The rack controller that will take over DHCP services if the primary fails."></span></dt><dd class="four-col last-col">{$ vlanDetails.secondaryRack.hostname $}</dd>
                         </div>
                         <dt class="two-col">Rack controllers <span class="icon icon--help tooltip" aria-label="A rack controller controls hosts and images and runs network services&#xa;like DHCP for connected VLANs."></span></dt>
 
=== modified file 'src/maasserver/testing/factory.py'
--- src/maasserver/testing/factory.py	2016-11-29 08:19:43 +0000
+++ src/maasserver/testing/factory.py	2016-12-06 08:04:41 +0000
@@ -1022,7 +1022,7 @@
 
     def make_VLAN(
             self, name=None, vid=None, fabric=None, dhcp_on=False,
-            primary_rack=None, secondary_rack=None):
+            primary_rack=None, secondary_rack=None, relay_vlan=None):
         assert vid != 0, "VID=0 VLANs are auto-created"
         if fabric is None:
             fabric = Fabric.objects.get_default_fabric()
@@ -1031,7 +1031,8 @@
             vid = self._get_available_vid(fabric)
         vlan = VLAN(
             name=name, vid=vid, fabric=fabric, dhcp_on=dhcp_on,
-            primary_rack=primary_rack, secondary_rack=secondary_rack)
+            primary_rack=primary_rack, secondary_rack=secondary_rack,
+            relay_vlan=relay_vlan)
         vlan.save()
         return vlan
 
 
=== modified file 'src/maasserver/tests/test_dhcp.py'
--- src/maasserver/tests/test_dhcp.py	2016-12-03 16:33:44 +0000
+++ src/maasserver/tests/test_dhcp.py	2016-12-06 08:04:41 +0000
@@ -17,7 +17,6 @@
     IPADDRESS_TYPE,
     SERVICE_STATUS,
 )
-from maasserver.exceptions import DHCPConfigurationError
 from maasserver.models import (
     Config,
     DHCPSnippet,
@@ -45,7 +44,6 @@
 from maastesting.twisted import (
     always_fail_with,
     always_succeed_with,
-    TwistedLoggerFixture,
 )
 from netaddr import (
     IPAddress,
@@ -422,8 +420,8 @@
                 rack_controller, vlan, subnet.get_ipnetwork().version))
 
 
-class TestGetManagedVLANsFor(MAASServerTestCase):
-    """Tests for `get_managed_vlans_for`."""
+class TestGenManagedVLANsFor(MAASServerTestCase):
+    """Tests for `gen_managed_vlans_for`."""
 
     def test__returns_all_managed_vlans(self):
         rack_controller = factory.make_RackController()
@@ -509,7 +507,31 @@
         self.assertEquals({
             vlan_one,
             vlan_two,
-        }, dhcp.get_managed_vlans_for(rack_controller))
+        }, set(dhcp.gen_managed_vlans_for(rack_controller)))
+
+    def test__returns_managed_vlan_with_relay_vlans(self):
+        rack_controller = factory.make_RackController()
+        vlan_one = factory.make_VLAN(
+            dhcp_on=True, primary_rack=rack_controller, name="1")
+        primary_interface = factory.make_Interface(
+            INTERFACE_TYPE.PHYSICAL, node=rack_controller, vlan=vlan_one)
+        managed_ipv4_subnet = factory.make_Subnet(
+            cidr=str(factory.make_ipv4_network().cidr), vlan=vlan_one)
+        factory.make_StaticIPAddress(
+            alloc_type=IPADDRESS_TYPE.STICKY, subnet=managed_ipv4_subnet,
+            interface=primary_interface)
+
+        # Relay VLANs atteched to the vlan.
+        relay_vlans = {
+            factory.make_VLAN(relay_vlan=vlan_one)
+            for _ in range(3)
+        }
+
+        # Should only contain the subnets that are managed by the rack
+        # controller and the best interface should have been selected.
+        self.assertEquals(
+            relay_vlans.union(set([vlan_one])),
+            set(dhcp.gen_managed_vlans_for(rack_controller)))
 
 
 class TestIPIsOnVLAN(MAASServerTestCase):
@@ -1300,31 +1322,6 @@
 class TestGetDHCPConfigureFor(MAASServerTestCase):
     """Tests for `get_dhcp_configure_for`."""
 
-    def test__raises_DHCPConfigurationError_for_ipv4(self):
-        primary_rack = factory.make_RackController()
-        secondary_rack = factory.make_RackController()
-
-        # VLAN for primary that has a secondary with multiple subnets.
-        ha_vlan = factory.make_VLAN(
-            dhcp_on=True, primary_rack=primary_rack,
-            secondary_rack=secondary_rack)
-        ha_subnet = factory.make_ipv4_Subnet_with_IPRanges(vlan=ha_vlan)
-        factory.make_Interface(
-            INTERFACE_TYPE.PHYSICAL, node=primary_rack, vlan=ha_vlan)
-        secondary_interface = factory.make_Interface(
-            INTERFACE_TYPE.PHYSICAL, node=secondary_rack, vlan=ha_vlan)
-        factory.make_StaticIPAddress(
-            alloc_type=IPADDRESS_TYPE.AUTO, subnet=ha_subnet,
-            interface=secondary_interface)
-        other_subnet = factory.make_ipv4_Subnet_with_IPRanges(vlan=ha_vlan)
-
-        ntp_servers = [factory.make_name("ntp")]
-        default_domain = Domain.objects.get_default_domain()
-        self.assertRaises(
-            DHCPConfigurationError, dhcp.get_dhcp_configure_for,
-            4, primary_rack, ha_vlan, [ha_subnet, other_subnet],
-            ntp_servers, default_domain)
-
     def test__returns_for_ipv4(self):
         primary_rack = factory.make_RackController()
         secondary_rack = factory.make_RackController()
@@ -1423,36 +1420,6 @@
             dhcp.make_hosts_for_subnets([ha_subnet]), observed_hosts)
         self.assertEqual(primary_interface.name, observed_interface)
 
-    def test__raises_DHCPConfigurationError_for_ipv6(self):
-        primary_rack = factory.make_RackController()
-        secondary_rack = factory.make_RackController()
-
-        # VLAN for primary that has a secondary with multiple subnets.
-        ha_vlan = factory.make_VLAN(
-            dhcp_on=True, primary_rack=primary_rack,
-            secondary_rack=secondary_rack)
-        ha_subnet = factory.make_Subnet(
-            vlan=ha_vlan, cidr="fd38:c341:27da:c831::/64")
-        factory.make_IPRange(
-            ha_subnet, "fd38:c341:27da:c831:0:1::",
-            "fd38:c341:27da:c831:0:1:ffff:0")
-        factory.make_Interface(
-            INTERFACE_TYPE.PHYSICAL, node=primary_rack, vlan=ha_vlan)
-        secondary_interface = factory.make_Interface(
-            INTERFACE_TYPE.PHYSICAL, node=secondary_rack, vlan=ha_vlan)
-        factory.make_StaticIPAddress(
-            alloc_type=IPADDRESS_TYPE.AUTO, subnet=ha_subnet,
-            interface=secondary_interface)
-        other_subnet = factory.make_Subnet(
-            vlan=ha_vlan, cidr="fd38:c341:27da:c832::/64")
-
-        ntp_servers = [factory.make_name("ntp")]
-        default_domain = Domain.objects.get_default_domain()
-        self.assertRaises(
-            DHCPConfigurationError, dhcp.get_dhcp_configure_for,
-            6, primary_rack, ha_vlan, [ha_subnet, other_subnet],
-            ntp_servers, default_domain)
-
     def test__returns_for_ipv6(self):
         primary_rack = factory.make_RackController()
         secondary_rack = factory.make_RackController()
@@ -1747,26 +1714,6 @@
 
     @wait_for_reactor
     @inlineCallbacks
-    def test__logs_DHCPConfigurationError_ipv4(self):
-        self.patch(dhcp.settings, "DHCP_CONNECT", True)
-        with TwistedLoggerFixture() as logger:
-            yield deferToDatabase(
-                self.create_rack_controller, missing_ipv4=True)
-            self.assertDocTestMatches(
-                "...No IPv4 interface...", logger.output)
-
-    @wait_for_reactor
-    @inlineCallbacks
-    def test__logs_DHCPConfigurationError_ipv6(self):
-        self.patch(dhcp.settings, "DHCP_CONNECT", True)
-        with TwistedLoggerFixture() as logger:
-            yield deferToDatabase(
-                self.create_rack_controller, missing_ipv6=True)
-            self.assertDocTestMatches(
-                "...No IPv6 interface...", logger.output)
-
-    @wait_for_reactor
-    @inlineCallbacks
     def test__doesnt_call_configure_for_both_ipv4_and_ipv6(self):
         # ... when DHCP_CONNECT is False.
         rack_controller, config = yield deferToDatabase(
 
=== modified file 'src/maasserver/tests/test_forms_vlan.py'
--- src/maasserver/tests/test_forms_vlan.py	2016-04-27 20:38:06 +0000
+++ src/maasserver/tests/test_forms_vlan.py	2016-12-06 08:04:41 +0000
@@ -8,6 +8,7 @@
 import random
 
 from maasserver.forms_vlan import VLANForm
+from maasserver.models.fabric import Fabric
 from maasserver.models.vlan import DEFAULT_MTU
 from maasserver.testing.factory import factory
 from maasserver.testing.testcase import MAASServerTestCase
@@ -27,6 +28,27 @@
                 ],
             }, form.errors)
 
+    def test__vlans_already_using_relay_vlan_not_shown(self):
+        fabric = Fabric.objects.get_default_fabric()
+        relay_vlan = factory.make_VLAN()
+        factory.make_VLAN(relay_vlan=relay_vlan)
+        form = VLANForm(fabric=fabric, data={})
+        self.assertItemsEqual(
+            [fabric.get_default_vlan(), relay_vlan],
+            form.fields['relay_vlan'].queryset)
+
+    def test__self_vlan_not_used_in_relay_vlan_field(self):
+        fabric = Fabric.objects.get_default_fabric()
+        relay_vlan = fabric.get_default_vlan()
+        form = VLANForm(instance=relay_vlan, data={})
+        self.assertItemsEqual([], form.fields['relay_vlan'].queryset)
+
+    def test__no_relay_vlans_allowed_when_dhcp_on(self):
+        vlan = factory.make_VLAN(dhcp_on=True)
+        factory.make_VLAN()
+        form = VLANForm(instance=vlan, data={})
+        self.assertItemsEqual([], form.fields['relay_vlan'].queryset)
+
     def test__creates_vlan(self):
         fabric = factory.make_Fabric()
         vlan_name = factory.make_name("vlan")
@@ -211,6 +233,54 @@
         vlan = reload_object(vlan)
         self.assertTrue(vlan.dhcp_on)
 
+    def test_update_sets_relay_vlan(self):
+        vlan = factory.make_VLAN()
+        relay_vlan = factory.make_VLAN()
+        form = VLANForm(instance=vlan, data={
+            "relay_vlan": relay_vlan.id,
+        })
+        self.assertTrue(form.is_valid(), form.errors)
+        form.save()
+        vlan = reload_object(vlan)
+        self.assertEquals(relay_vlan.id, vlan.relay_vlan.id)
+
+    def test_update_clears_relay_vlan_when_None(self):
+        relay_vlan = factory.make_VLAN()
+        vlan = factory.make_VLAN(relay_vlan=relay_vlan)
+        form = VLANForm(instance=vlan, data={
+            "relay_vlan": None,
+        })
+        self.assertTrue(form.is_valid(), form.errors)
+        form.save()
+        vlan = reload_object(vlan)
+        self.assertIsNone(vlan.relay_vlan)
+
+    def test_update_clears_relay_vlan_when_empty(self):
+        relay_vlan = factory.make_VLAN()
+        vlan = factory.make_VLAN(relay_vlan=relay_vlan)
+        form = VLANForm(instance=vlan, data={
+            "relay_vlan": "",
+        })
+        self.assertTrue(form.is_valid(), form.errors)
+        form.save()
+        vlan = reload_object(vlan)
+        self.assertIsNone(vlan.relay_vlan)
+
+    def test_update_disables_relay_vlan_when_dhcp_turned_on(self):
+        relay_vlan = factory.make_VLAN()
+        vlan = factory.make_VLAN(relay_vlan=relay_vlan)
+        factory.make_ipv4_Subnet_with_IPRanges(vlan=vlan)
+        rack = factory.make_RackController(vlan=vlan)
+        vlan.primary_rack = rack
+        vlan.save()
+        form = VLANForm(instance=reload_object(vlan), data={
+            "dhcp_on": "true",
+        })
+        self.assertTrue(form.is_valid(), form.errors)
+        form.save()
+        vlan = reload_object(vlan)
+        self.assertIsNone(vlan.relay_vlan)
+
     def test_update_validates_primary_rack_with_dhcp_on(self):
         vlan = factory.make_VLAN()
         form = VLANForm(instance=vlan, data={
 
=== modified file 'src/maasserver/triggers/system.py'
--- src/maasserver/triggers/system.py	2016-10-12 15:26:17 +0000
+++ src/maasserver/triggers/system.py	2016-12-06 08:04:41 +0000
@@ -268,6 +268,8 @@
 DHCP_VLAN_UPDATE = dedent("""\
     CREATE OR REPLACE FUNCTION sys_dhcp_vlan_update()
     RETURNS trigger as $$
+    DECLARE
+      relay_vlan maasserver_vlan;
     BEGIN
       -- DHCP was turned off.
       IF OLD.dhcp_on AND NOT NEW.dhcp_on THEN
@@ -303,6 +305,60 @@
           PERFORM pg_notify(CONCAT('sys_dhcp_', NEW.secondary_rack_id), '');
         END IF;
       END IF;
+
+      -- Relay VLAN was set when it was previously unset.
+      IF OLD.relay_vlan_id IS NULL AND NEW.relay_vlan_id IS NOT NULL THEN
+        SELECT maasserver_vlan.* INTO relay_vlan
+        FROM maasserver_vlan
+        WHERE maasserver_vlan.id = NEW.relay_vlan_id;
+        IF relay_vlan.primary_rack_id IS NOT NULL THEN
+          PERFORM pg_notify(
+            CONCAT('sys_dhcp_', relay_vlan.primary_rack_id), '');
+          IF relay_vlan.secondary_rack_id IS NOT NULL THEN
+            PERFORM pg_notify(
+              CONCAT('sys_dhcp_', relay_vlan.secondary_rack_id), '');
+          END IF;
+        END IF;
+      -- Relay VLAN was unset when it was previously set.
+      ELSIF OLD.relay_vlan_id IS NOT NULL AND NEW.relay_vlan_id IS NULL THEN
+        SELECT maasserver_vlan.* INTO relay_vlan
+        FROM maasserver_vlan
+        WHERE maasserver_vlan.id = OLD.relay_vlan_id;
+        IF relay_vlan.primary_rack_id IS NOT NULL THEN
+          PERFORM pg_notify(
+            CONCAT('sys_dhcp_', relay_vlan.primary_rack_id), '');
+          IF relay_vlan.secondary_rack_id IS NOT NULL THEN
+            PERFORM pg_notify(
+              CONCAT('sys_dhcp_', relay_vlan.secondary_rack_id), '');
+          END IF;
+        END IF;
+      -- Relay VLAN has changed on the VLAN.
+      ELSIF OLD.relay_vlan_id != NEW.relay_vlan_id THEN
+        -- Alert old VLAN if required.
+        SELECT maasserver_vlan.* INTO relay_vlan
+        FROM maasserver_vlan
+        WHERE maasserver_vlan.id = OLD.relay_vlan_id;
+        IF relay_vlan.primary_rack_id IS NOT NULL THEN
+          PERFORM pg_notify(
+            CONCAT('sys_dhcp_', relay_vlan.primary_rack_id), '');
+          IF relay_vlan.secondary_rack_id IS NOT NULL THEN
+            PERFORM pg_notify(
+              CONCAT('sys_dhcp_', relay_vlan.secondary_rack_id), '');
+          END IF;
+        END IF;
+        -- Alert new VLAN if required.
+        SELECT maasserver_vlan.* INTO relay_vlan
+        FROM maasserver_vlan
+        WHERE maasserver_vlan.id = NEW.relay_vlan_id;
+        IF relay_vlan.primary_rack_id IS NOT NULL THEN
+          PERFORM pg_notify(
+            CONCAT('sys_dhcp_', relay_vlan.primary_rack_id), '');
+          IF relay_vlan.secondary_rack_id IS NOT NULL THEN
+            PERFORM pg_notify(
+              CONCAT('sys_dhcp_', relay_vlan.secondary_rack_id), '');
+          END IF;
+        END IF;
+      END IF;
       RETURN NEW;
     END;
     $$ LANGUAGE plpgsql;
 
=== modified file 'src/maasserver/triggers/tests/test_system_listener.py'
--- src/maasserver/triggers/tests/test_system_listener.py	2016-10-12 15:26:17 +0000
+++ src/maasserver/triggers/tests/test_system_listener.py	2016-12-06 08:04:41 +0000
@@ -806,6 +806,120 @@
         finally:
             yield listener.stopService()
 
+    @wait_for_reactor
+    @inlineCallbacks
+    def test_sends_messages_when_relay_vlan_set(self):
+        yield deferToDatabase(register_system_triggers)
+        primary_rack = yield deferToDatabase(self.create_rack_controller)
+        secondary_rack = yield deferToDatabase(self.create_rack_controller)
+        relay_vlan = yield deferToDatabase(self.create_vlan, params={
+            "dhcp_on": True,
+            "primary_rack": primary_rack,
+            "secondary_rack": secondary_rack,
+        })
+        vlan = yield deferToDatabase(self.create_vlan)
+        primary_rack_dv = DeferredValue()
+        secondary_rack_dv = DeferredValue()
+        listener = self.make_listener_without_delay()
+        listener.register(
+            "sys_dhcp_%s" % primary_rack.id,
+            lambda *args: primary_rack_dv.set(args))
+        listener.register(
+            "sys_dhcp_%s" % secondary_rack.id,
+            lambda *args: secondary_rack_dv.set(args))
+        yield listener.startService()
+        try:
+            yield deferToDatabase(self.update_vlan, vlan.id, {
+                "relay_vlan": relay_vlan,
+            })
+            yield primary_rack_dv.get(timeout=2)
+            yield secondary_rack_dv.get(timeout=2)
+        finally:
+            yield listener.stopService()
+
+    @wait_for_reactor
+    @inlineCallbacks
+    def test_sends_messages_when_relay_vlan_unset(self):
+        yield deferToDatabase(register_system_triggers)
+        primary_rack = yield deferToDatabase(self.create_rack_controller)
+        secondary_rack = yield deferToDatabase(self.create_rack_controller)
+        relay_vlan = yield deferToDatabase(self.create_vlan, params={
+            "dhcp_on": True,
+            "primary_rack": primary_rack,
+            "secondary_rack": secondary_rack,
+        })
+        vlan = yield deferToDatabase(self.create_vlan, {
+            "relay_vlan": relay_vlan,
+        })
+        primary_rack_dv = DeferredValue()
+        secondary_rack_dv = DeferredValue()
+        listener = self.make_listener_without_delay()
+        listener.register(
+            "sys_dhcp_%s" % primary_rack.id,
+            lambda *args: primary_rack_dv.set(args))
+        listener.register(
+            "sys_dhcp_%s" % secondary_rack.id,
+            lambda *args: secondary_rack_dv.set(args))
+        yield listener.startService()
+        try:
+            yield deferToDatabase(self.update_vlan, vlan.id, {
+                "relay_vlan": None,
+            })
+            yield primary_rack_dv.get(timeout=2)
+            yield secondary_rack_dv.get(timeout=2)
+        finally:
+            yield listener.stopService()
+
+    @wait_for_reactor
+    @inlineCallbacks
+    def test_sends_messages_when_relay_vlan_changed(self):
+        yield deferToDatabase(register_system_triggers)
+        old_primary_rack = yield deferToDatabase(self.create_rack_controller)
+        old_secondary_rack = yield deferToDatabase(self.create_rack_controller)
+        old_relay_vlan = yield deferToDatabase(self.create_vlan, params={
+            "dhcp_on": True,
+            "primary_rack": old_primary_rack,
+            "secondary_rack": old_secondary_rack,
+        })
+        new_primary_rack = yield deferToDatabase(self.create_rack_controller)
+        new_secondary_rack = yield deferToDatabase(self.create_rack_controller)
+        new_relay_vlan = yield deferToDatabase(self.create_vlan, params={
+            "dhcp_on": True,
+            "primary_rack": new_primary_rack,
+            "secondary_rack": new_secondary_rack,
+        })
+        vlan = yield deferToDatabase(self.create_vlan, {
+            "relay_vlan": old_relay_vlan,
+        })
+        old_primary_rack_dv = DeferredValue()
+        old_secondary_rack_dv = DeferredValue()
+        new_primary_rack_dv = DeferredValue()
+        new_secondary_rack_dv = DeferredValue()
+        listener = self.make_listener_without_delay()
+        listener.register(
+            "sys_dhcp_%s" % old_primary_rack.id,
+            lambda *args: old_primary_rack_dv.set(args))
+        listener.register(
+            "sys_dhcp_%s" % old_secondary_rack.id,
+            lambda *args: old_secondary_rack_dv.set(args))
+        listener.register(
+            "sys_dhcp_%s" % new_primary_rack.id,
+            lambda *args: new_primary_rack_dv.set(args))
+        listener.register(
+            "sys_dhcp_%s" % new_secondary_rack.id,
+            lambda *args: new_secondary_rack_dv.set(args))
+        yield listener.startService()
+        try:
+            yield deferToDatabase(self.update_vlan, vlan.id, {
+                "relay_vlan": new_relay_vlan,
+            })
+            yield old_primary_rack_dv.get(timeout=2)
+            yield old_secondary_rack_dv.get(timeout=2)
+            yield new_primary_rack_dv.get(timeout=2)
+            yield new_secondary_rack_dv.get(timeout=2)
+        finally:
+            yield listener.stopService()
+
 
 class TestDHCPSubnetListener(
         MAASTransactionServerTestCase, TransactionalHelpersMixin):
 
=== modified file 'src/maasserver/websockets/handlers/tests/test_vlan.py'
--- src/maasserver/websockets/handlers/tests/test_vlan.py	2016-10-19 18:06:01 +0000
+++ src/maasserver/websockets/handlers/tests/test_vlan.py	2016-12-06 08:04:41 +0000
@@ -42,6 +42,7 @@
             "external_dhcp": vlan.external_dhcp,
             "primary_rack": vlan.primary_rack,
             "secondary_rack": vlan.secondary_rack,
+            "relay_vlan": vlan.relay_vlan_id,
         }
         data['rack_sids'] = sorted(list({
             interface.node.system_id
@@ -206,6 +207,20 @@
         self.assertThat(vlan.primary_rack, Is(None))
         self.assertThat(vlan.secondary_rack, Is(None))
 
+    def test__configure_dhcp_with_relay_vlan(self):
+        user = factory.make_admin()
+        handler = VLANHandler(user, {})
+        vlan = factory.make_VLAN()
+        relay_vlan = factory.make_VLAN()
+        handler.configure_dhcp({
+            "id": vlan.id,
+            "controllers": [],
+            "relay_vlan": relay_vlan.id,
+        })
+        vlan = reload_object(vlan)
+        self.assertThat(vlan.dhcp_on, Equals(False))
+        self.assertThat(vlan.relay_vlan, Equals(relay_vlan))
+
     def test__non_superuser_asserts(self):
         user = factory.make_User()
         handler = VLANHandler(user, {})
 
=== modified file 'src/maasserver/websockets/handlers/vlan.py'
--- src/maasserver/websockets/handlers/vlan.py	2016-10-20 19:39:48 +0000
+++ src/maasserver/websockets/handlers/vlan.py	2016-12-06 08:04:41 +0000
@@ -104,6 +104,10 @@
             NODE_PERMISSION.ADMIN, vlan), "Permission denied."
         vlan.delete()
 
+    def update(self, parameters):
+        """Delete this VLAN."""
+        return super(VLANHandler, self).update(parameters)
+
     def _configure_iprange_and_gateway(self, parameters):
         if 'subnet' in parameters and parameters['subnet'] is not None:
             subnet = Subnet.objects.get(id=parameters['subnet'])
@@ -171,18 +175,21 @@
         # of parameters, to prevent spurious log statements.
         if 'extra' in parameters:
             self._configure_iprange_and_gateway(parameters['extra'])
-        iprange_count = IPRange.objects.filter(
-            type=IPRANGE_TYPE.DYNAMIC, subnet__vlan=vlan).count()
-        if iprange_count == 0:
-            raise ValueError(
-                "Cannot configure DHCP: At least one dynamic range is "
-                "required.")
+        if 'relay_vlan' not in parameters:
+            iprange_count = IPRange.objects.filter(
+                type=IPRANGE_TYPE.DYNAMIC, subnet__vlan=vlan).count()
+            if iprange_count == 0:
+                raise ValueError(
+                    "Cannot configure DHCP: At least one dynamic range is "
+                    "required.")
         controllers = parameters.get('controllers', [])
         data = {
             "dhcp_on": True if len(controllers) > 0 else False,
             "primary_rack": controllers[0] if len(controllers) > 0 else None,
             "secondary_rack": controllers[1] if len(controllers) > 1 else None,
         }
+        if 'relay_vlan' in parameters:
+            data['relay_vlan'] = parameters['relay_vlan']
         form = VLANForm(instance=vlan, data=data)
         if form.is_valid():
             form.save()