Multicast issues (including ipv6 neighbor discovery)

[vihai]

Hello,

I've read:

https://forum.proxmox.com/threads/linux-bridge-vlan-multicast.114036/
https://forum.proxmox.com/threads/multicast-bridge-problem.107410/

I seem to be experiencing the same issue.

My setup is the following:
- 6 hosts with a bunch of VMs each, latest 5.13.19-6-pve kernel and PVE (7.3-4) version.
- a VM hosting a (Mikrotik...) firewall and routing between VLANs.
- VLAN-aware bridge
- IPv6 configured everywhere

While the firewall was on a separate box I experienced no issue.

After moving the firewall in a VM I had intermittent issues that were resolved reconfiguring the network on the VM or rebooting, or removing/adding the IPv6 address on the firewall.

After few days the IPv6 connectivity started breaking apart with neighbor being discovered between some VMs and not between others.

After rebooting the firewall the issue got even worse.

The firewall couldn't resolve most of its neighbors.
The VMs did not receive neighbor solicitation

Reconfiguring the nework on a VM somewhat fixed its issues.

Everything started working again after disabling multicast_snooping on all the hosts.

echo 0 > /sys/devices/virtual/net/vmbr0/bridge/multicast_snooping

 

[adamreece.webbox]

Thank you very much for this tip. This instantly resolved a whole host of IPv6 issues we've been having within ProxMox and guests.

I also noticed that this has corrected WS-Discovery. Guest VMs now discover instantly.

 

[erazmus]

This has fixed our IPv6 problem that has been plaguing us for weeks. Thank you!