RouterOS version: 7.22.2
RouterBOARD firmware: 7.22.2
I’m running into an MLAG issue with a setup that has three MLAG pairs.
The issue only happens on the right-side MLAG pair (SW04: CRS520-4XS-16XQ + SW05: CRS520-4XS-16XQ) This pair is connected upstream to SW01/SW06 using bonding3.
When edge=no is configured on bonding3 on SW04/SW05, the MLAG pair breaks after a topology change or after rebooting one of the other switches in the topology, for example: SSW01 / SSW02 / SW01 / SW06.
After this happens, SW04/SW05 do not recover by themselves. The only way I have found to restore the MLAG pair is to reboot either SW04 or SW05.
If I set edge=yes on bonding3, the issue seems to be mitigated. However, I do not think this is the correct setting, because bonding3 is a core/uplink connection, not an edge/access port.
My questions:
-
Is
edge=nothe correct setting for an MLAG/core/uplink bond like this? -
Could this be a RouterOS MLAG/STP issue, or am I missing something in the configuration?
One thing I find really odd is that this only seems to happen with the MLAG pair that consists of 2x CRS520-4XS-16XQ.
The center MLAG pair, which is CRS520-4XS-16XQ + CRS326-24S+2Q+, does not show the same symptoms in the same topology.
So far the issue appears to be specific to the CRS520 + CRS520 MLAG pair. Any ideas or suggestions are welcome.
UPDATE(Official Mikrotik support reply):
"We have managed to reproduce the issue locally in our labs and look forward to fixing it on upcoming RouterOS versions, unfortunately, I cannot provide a release date now.
The underlying issue is that RouterOS MLAG currently does not synchronize the STP port states on dual-connected bonds. Using edge=auto is workaround as you already found out"