port channel and spanning tree on nexus 5000 switch

Enrico Rinero · ‎09-30-2016

Hi,

I have a couples of Cisco Nexus 5000 switches connected client side with a couple of 7613 routers (with four different vlans, for example) working in active active mode; Cisco 7613 routers are not running spanning tree and work as a layer 3 device.

Server side, Nexus are connected to a couple of load balancers, LB working in active backup mode, and they are not running spanning tree too.

Nexus Switches are configured as layer 2 devices, working in active active mode.

Is not a full mesh topology: 7613-1 to / from nexus-1; nexus-1 to / from load balancer 1.

7613-2 to / from nexus-2; nexus 2 to / from load balancer-2.

I configure a back to back interface between nexus 1 and nexus 2 with a port channel, two physical links and 4 vlans per link. Do I need running spanning tree between these back to back link or I can avoid spanning tree at all? Note that the same vlans are configured in the port channel interface from nexus to 7613-1 and 7613-2, but not in the interlink/port channel between the two 7613 routers; and from nexus to the load balancer, but not in the interlink between the two load balancers.

Best Regards.

cwhite0013 · ‎10-01-2016

So, it sounds like the only layer 2 connection between switches is the port-channel between nexus-1 and nexus-2. Spanning-tree is only going to be active on the virtual port-channel interface and won't block any ports since there is no loop. So, technically, in this case, you don't NEED spanning-tree because there is no loop but I'd STRONGLY recommend leaving it enabled encase someone accidentally causes a loop or if something happens to the LACP process (unlikely but possible), the two physical ports wont cause a loop.

Enrico Rinero · ‎10-03-2016

Hi I attach this architecture.

So you think could be useful activating spanning tree between back to back link Switch 1 - Switch 2, even if this is a Port Channel so is considered as a single link?

I have not activated spanning tree processes citrix side or cisco 7613 side.

Best Regards, Enrico Rinero