Nexus 5000/Fabric Extender 2000 Design question / limitations

markuswirth85 · ‎06-09-2010

Hello everyone!

I got a question concerning two Nexus 5020 and two Fabrix Extender 2000.

The Topology is quite easy. I have the two Nexus 5020 formed to a vPC-Domain and now there are two possibilities to connect the FEXs.

1st:

Each Fabric Extender is connected to a single Nexus 5020 with 2x10G. Everything should work fine but there is no redundancy for the FEXs if one Nexus 5020 goes down.

2nd:

Each FEX is connected with 1x10G to each of the both Nexus 5020 so that there is cabling redundancy. The Nexus 5020 connect to the FEX via a vPC.

Both solutions work BUT....

...with the 1st solution it is possible that I can form a LACP Etherchannel from a Server with two NICs to the FEXs. One Port of the Server on the one FEX and one on the other. The Server has a Full Etherchannel to the Switches.

Now the question:

Is it possible to do this also with the FEXs cross-connected to the Nexus 5020 like in solution No.2? In the Cisco documentation it seems that this seems not to work and seems to be a restriction.

Thanks in advance!

Regards! Markus.

David Lucas · ‎08-31-2010

Hello Markus,

Sorry for the delay on this, I just came across it and didn't see that anyone replied.

If the FEX is dual homed to the 5ks utilizing VPC for FEX connectivity then you will NOT be able to do Active/Active to the server only Active Standby. If the FEX is attached to only one 5k then you'll be able to do a Active/Active utilizing VPC to the server. Think of it this way, you can do a VPC to a Nexus 7k for upstream connectivity and you are currently only allowed to do one VPC for downstream connectivity. Either that downstream VPC be used for FEX connectivity or Active/Active server connectivity.

Hope that clarifies.

Dave