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mike7
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RB5009 ROS 7.1.1 IGMP Snooping issue with L2 HW offload

Mon Jan 17, 2022 7:24 am

ipv6 RA multicast stops work with IGMP Snooping enabled on RB5009. Bridge configured with L2 hw offload.

Steps to reproduce:
  • enable L2 hw offload on bridge ports
  • enable IGMP Snooping
  • set short ra-lifetime and reachable-time in ipv6 ND config, reduce ra-interval
as result ipv6 addresses will expire on clients soon, looks like router stops to send RA multicast

Disabling the L2 hw offloading solves the issue, but IGMP Proxy still working unstable.

Both 7.1.1 and 7.2rc1 have the issue
 
Ady262
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Re: RB5009 ROS 7.1.1 IGMP Snooping issue with L2 HW offload  [SOLVED]

Mon Jan 17, 2022 12:32 pm

Hi, I had a similar problem on my RB5009, multicast stopped working after about 5 minutes then I had to call the multicast query again. I solved this problem by enabling "Multicast Querier" on the bridge. After this procedure it started working correctly. I was previously using RB760 and did not have this option enabled and it worked fine.
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mike7
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Re: RB5009 ROS 7.1.1 IGMP Snooping issue with L2 HW offload

Tue Jan 18, 2022 7:34 am

I solved this problem by enabling "Multicast Querier" on the bridge.
Thank you it is working fine, also it is mentioned in the docs https://help.mikrotik.com/docs/pages/vi ... figuration

Still have some issues with IGM proxy but it is different story, I can't find the way how to reproduce.
 
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jbl42
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Re: RB5009 ROS 7.1.1 IGMP Snooping issue with L2 HW offload

Tue Jan 18, 2022 3:02 pm

Just be aware that the ROS bridge IGMP querier is not VLAN aware:
Only untagged IGMP/MLD general membership queries are generated, IGMP queries are sent with IPv4 0.0.0.0 source address, MLD queries are sent with IPv6 link-local address of the bridge interface. The bridge will not send queries if an external IGMP/MLD querier is detected (see the monitoring values igmp-querier and mld-querier).
If you have VLAN filtering active on the bridge with IGMP snooping, learning and multicst forwarding properly works per VLAN, as visible in the MDB stats of the bridge.
But if the bridge acts as querier, the generated IGMP queries are always sent untagged. So if you have multicast clients on the bridge on tagged VLANs, they will not receive queries and those multicast forwards still will time out.
There are also multicast devices silently dropping IGMP queries comming from IP source 0.0.0.0.
This is quite a stupid limitation, which might be fixed in a future version according to MT support.
 
mike7
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Re: RB5009 ROS 7.1.1 IGMP Snooping issue with L2 HW offload

Tue Jan 18, 2022 3:28 pm

The issue was with ipv6 RA packets, I have no idea how it depends on IGMP querier and L2 HW offload.
 
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jbl42
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Re: RB5009 ROS 7.1.1 IGMP Snooping issue with L2 HW offload

Tue Jan 18, 2022 3:52 pm

AFAIK ipv6 RA is using ipv6 mcast group ff02::2. This is link-local and as such according to the docs always flooded, independant of MLD snooping.
But still it seems the MLD querier is required to keep the ff02::2 MDB entries alive when L2 hw offload is enabled.

With bridge L2 hw offload multicast learning/forwarding is handled by the RB5009 switch chip, without by ROS bridge SW on the CPU.
IMHO the ROS SW behaviour without L2 hw offload is correct (not requiring a querier for link local groups as they are flooded)

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