Wednesday, 4 March 2015

FEXs on a Nexus 7010

I've been considering how to deal with connecting our Aruba wireless controllers, when we switch over the Nexus stuff - they're currently linked directly to our existing Catalyst 6509-Es in the data centre, so we need to do something, even in the interim.  One solution that looks sensible is FEXs attached directly to the Nexus 7010s, so I thought I'd give that a quick try, as I've so far done this on the 56128Ps, only.

First difference is that the FEX functionality must be installed before it can be activated as a feature - similar to MPLS.  This must be done in the admin VDC, then it can be activated in the local VDC:

n7k-top# conf t
Enter configuration commands, one per line.  End with CNTL/Z.
n7k-top(config)# install feature-set fex
n7k-top(config)# end
n7k-top# switchto vdc srv
n7k-top-srv# conf t
Enter configuration commands, one per line.  End with CNTL/Z.
n7k-top-srv(config)# feature-set fex

From then on, things work pretty much as they do on the 56128Ps.

However, one important difference is that it seems not to be possible to use vPC on a FEX fabric port, unlike a 56128P, at least on NX-OS 6.2:

n7k-top-srv(config)# int e1/24
n7k-top-srv(config-if)# channel-group 102

n7k-top-srv(config)# int po102
n7k-top-srv(config-if)# switchport mode fex-fabric 
n7k-top-srv(config-if)# fex associate 102
n7k-top-srv(config-if)# vpc 102 
ERROR: Operation failed: [FEX interface is not capable of acting as vPC] 

This means it's not possible to dual-attach FEXs to two 7010s.  However, it is possible to create a vPC across two FEXs attach to 7ks which themselves are acting as a vPC pair: any devices wanting redundancy on these will need to attach to two FEXs.

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