PVE 8.2.5 neighbour discovery not working sometimes

[CanadaGuy]

Hi, I've had a situation where my router sends NDP packets to the VMs on my PVE host. They are never received (detected with tcpdump) by some hosts, but other hosts seem to continue functioning just fine.

If I fiddle with SOMEthing on PVE (I'm not sure what yet) it starts working until something times out. Today's "fiddle" was starting a PVE backup script from the Datacenter node, and all of a sudden IPv6 packets start flowing again for a period of time. If I leave it alone for a while, it'll stop working again and the cycle continues.

My next steps are to monitor the PVE host with tcpdump the next time communication stops again. Any specifics I can poke at?

 

[meyergru]

Probably not a new issue: https://forum.proxmox.com/threads/ipv6-neighbor-solicitation-not-forwarded-to-vm.96758/

This one had me good as well. I found that in the first few minutes after boot, everything works fine until it does not. If you disable mulicast snooping on the bridge, it suddenly works.

 

[CanadaGuy]

okay, thanks! Of course, right now, everything is working so I'm waiting for that to stop, then I'll try that change.

 

[CanadaGuy]

Just tried it with a ping running from a few subnets...that fixed it right up! Thank you so much!