[openstack-dev] [neutron] Enable arp_responder without l2pop

Anil Venkata anilvenkata at redhat.com
Wed Feb 22 03:47:46 UTC 2017

Hi All

Currently arp_resonder can enabled only if l2pop is enabled.

Can we have arp_responder feature enabled without l2pop(i.e Remove the
dependency between arp_responder and l2_pop)?
Also setup arp_responder on OVS integration bridge(and not on br-tun)?.

To enable arp_responder, we only need port's MAC and IP Address and no
tunnel ip(So no need for l2pop).
Currently agents use l2pop notifications to create ARP entries. With the
new approach, agents can use
port events(create, update and delete) to create ARP entry and without
l2pop notifications.

The advantages with this approach for both linuxbridge and OVS agent -
1) Users can enable arp_responder without l2pop
2) Support ARP for distributed router ports(DVR and HA).
    Currently, ARP is not added for these ports.
    This is a fix for https://bugs.launchpad.net/neutron/+bug/1661717

As we are not dependent on l2pop, we can  create ARP entries on OVS
integration bridge.

Advantages for OVS agent, if ARP entries are setup on integration
bridge(br-int) rather than on tunneling bridge(br-tun)
1) It enables arp_responder for all network types(vlans, vxlan, etc)
    arp_responder based on l2pop is supported for only overlay networks.
2) ARP can be resolved within br-int.
3) ARP packets for local ports(ports connected to same br-int) will be
   in br-int without broadcasting to actual ports connected to br-int.

Any suggestions?

Also submitted bug [1] for this.

[1] https://bugs.launchpad.net/neutron/+bug/1518392

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