topic Re: What happens if a Stack is broken? in ExtremeSwitching (EXOS/Switch Engine)

What happens if a Stack is broken?

Alexander_Bauer — Wed, 15 May 2019 15:36:15 GMT

Hi,

does anybody know what happens with the clients of a dual stack if the stack is broken and we have a split brain situation with two master? We use the X440-G2 Switches with 22.6 EXOS conneced to MLAG Peers.

Is there a solution to keep one of the switches online without disrupting the network?

Thanks,

Alex

Re: What happens if a Stack is broken?

OscarK — Wed, 15 May 2019 20:29:18 GMT

If both stack members are master capable both will become master.
If the uplink to the MLAG core switches has one port on each slot then one of the links will remain active and the other not as LACP will negotiate with only 1 partner.
One slot will keep working while the other would work but will have no uplink.

Re: What happens if a Stack is broken?

Alexander_Bauer — Wed, 15 May 2019 20:46:54 GMT

Thanks for your answer.
Yes every slot has one uplink to one MLAG Peer with LACP.
Sure that one slot will working well, even though the Slots have the same IP and Stacking MAC?
I think the MLAG Cores will become in trouble because of that.

Re: What happens if a Stack is broken?

OscarK — Wed, 15 May 2019 20:49:20 GMT

Hi Alexander, one of the LACP links will be a member of the LAG on the cores, the other would not be a member, that is what I expect.
The core switch will see 2 links going to the same mac but as the stack slots dont communicate the LACP negotiation will fail for using both links and only 1 will be active, that is what I expect to happen.