[openstack-dev] [neutron][IPv6] Neighbor Discovery for HA

Robert Li (baoli) baoli at cisco.com
Wed Aug 27 13:33:49 UTC 2014

Hi Xuhan,

What I saw is that GARP is sent to the gateway port and also to the router ports, from a neutron router. I’m not sure why it’s sent to the router ports (internal network). My understanding for arping to the gateway port is that it is needed for proper NAT operation. Since we are not planning to support ipv6 NAT, so this is not required/needed for ipv6 any more?

There is an abandoned patch that disabled the arping for ipv6 gateway port:  https://review.openstack.org/#/c/77471/3/neutron/agent/l3_agent.py


On 8/27/14, 1:03 AM, "Xuhan Peng" <pengxuhan at gmail.com<mailto:pengxuhan at gmail.com>> wrote:

As a follow-up action of yesterday's IPv6 sub-team meeting, I would like to start a discussion about how to support l3 agent HA when IP version is IPv6.

This problem is triggered by bug [1] where sending gratuitous arp packet for HA doesn't work for IPv6 subnet gateways. This is because neighbor discovery instead of ARP should be used for IPv6.

My thought to solve this problem turns into how to send out neighbor advertisement for IPv6 routers just like sending ARP reply for IPv4 routers after reading the comments on code review [2].

I searched for utilities which can do this and only find a utility called ndsend [3] as part of vzctl on ubuntu. I could not find similar tools on other linux distributions.

There are comments in yesterday's meeting that it's the new router's job to send out RA and there is no need for neighbor discovery. But we didn't get enough time to finish the discussion.

Can you comment your thoughts about how to solve this problem in this thread, please?

[1] https://bugs.launchpad.net/neutron/+bug/1357068

[2] https://review.openstack.org/#/c/114437/

[3] http://manpages.ubuntu.com/manpages/oneiric/man8/ndsend.8.html

Xu Han
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