Setting STP properly or disabling at all in MLAG setup

[Robert_Zdzieblo]

Hello Guys,

I got a customer with MLAG’ed stacks as peers (X670-G2 and X460-G2 in each stack), where the edge switches are X440-G2 stacks, LAGged to both peers. So the whole environment is EXOS.

When I upgraded from 22.3 to 22.5 I got LAG uplink ports (master) on edge stacks set to blocked.

Command “debug vlan show vpif default 1:52” run on edge stack showed that STP was registered on the port.

Before the upgrade to 22.5 I didn’t setup STP in any way, although it was enabled by defalut AFAIK.

After the upgrade I tried to disable stpd on edge stacks, but it didn’t help.

As we had a downtime in production network,  there was no time for further troubleshooting and we have to revert to 22.3, which resulted in getting network up and working again.

I haven’t disabled STP on MLAG ports at MLAG peers when running 22.5, as I have no time.

I know that RSTP support for MLAG was introduced in ExtremeXOS 22.5 and that changed the way STP works in my setup.

Do you think disabling STP on MLAG ports at peers would help in this case ?

BEST REGARDS

Robert

[Robert_Zdzieblo]

Thank you, Gabriel !

So I am going to disable stp on MLAG ports:

disable stpd s0 ports <All_MLAG_ports_on_peers>

and on access stacks:

disable stpd s0 ports <Sharing_Master_port> 

Or even disable stp completely:

disable stpd 

on both MLAG peers and access stacks.

For loop protection I would rather use ELRP on MLAG peers.

Does it make sense ?

REGARDS 

Robert 

[Gabriel_G]

Hi Robert,

You are correct, the MLAG ports on the peer stacks and the LAG ports on the remote switch should not be in the blocking state. Removing these ports from all STP instances will likely fix your issue, however, I would double check your VLANs and their associated ports as wells as your STP config to ensure that there isn’t an additional loop in your network causing this issue.

For reference, see this article for STP requirements for an MLAG setup, this article for an example configuration, and this article for MLAG with RSTP limitations and configuration.

Regards,

Gabriel