UCS - East West Switching..Not Working I think

[chrisstylesweb]

Hi all hope you can shed some light.

I understood that the FI's switch east west traffic, Had an issue tonight where we removed Unplugged the north south portchannels to the layer3 network to upgrade the core and all VM's in the UCS lost connectivity to each other even though they are on the same VLAN.

So question is should downing the uplinks really stop east west switching?

Hope you can shed some light,

Thanks

[Walter Dey · Accepted solution]

Assuming End host mode for Ethernet: f you have vnic of the originator connected to fabric A, the vnic of the destination to fabric B, both on the same Vlan; then your traffic will have to exit the UCS domain Northbound, and reenter UCS on the other fabric.

Switching on the FI-A only happens, if same Van and initiator and target vnic on this fabric A.

Hope this clarifies your situation.

[chrisstylesweb]

wdey, Thanks for your reply.

End host mode is correct and all Vlans are dual, so yes I see your point with no route between the fabric, some traffic would stop.

The actual "Everything down" issue came from the network control policy "Action on Uplink Fail" being set to Link down. This basically downed the vnics and caused the mild panic, as I understand this needs to be set so that fabric failover will work.

I'll be attempting the swapout again with it set to Warning during the swap so as to try and minimise disruption.

Thanks again.

[Walter Dey]

OK, thanks ! You agree, that if NIC teaming and / or FC multipathing is working, UCS should keep working, if one fabric goes down ! despite the action on uplink fail = link down. All the vnics for all the chassis would be on the remaining fabric, and East - West traffic should work smoothly.