Can you use a BACKUP port when using VSS

Unanswered Question
Nov 3rd, 2009

We are going to move to VSS, and some of the blade servers we have don't support VBS, so I can run MEC to the switches. I would like to use switch ports in the BACKUP config.

Router(config-if)# switchport backup interface fastethernet 4/1

With changes VSS does to STP, can the BACKUP command still be used?

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Giuseppe Larosa Fri, 11/06/2009 - 00:30

Hello Cody,

multi chassis etherchannel should be the best choice for connecting to a VSS because it allows to use both links.

with the backup option it is like connecting to two standalone chassis.

in a recent thread about VSS advantages several colleagues have pointed out that with VSS you can use both uplinks doubling the BW.

Hope to help


melcara Mon, 11/23/2009 - 14:27

the issue is the Blade switches can't stack, so I need to prevent a STP loop.  So I figured the backup port would be the best option.

Giuseppe Larosa Mon, 11/23/2009 - 15:08

Hello Cody,

but  your blade switches are interconnected between themselves or only with VSS?

in latter case you should be able to setup an etherchannel for each blade to VSS without any problem also in case one of the two chassis in the VSS pair fails.

in my understanding MEC is multi-chassis on the VSS side.


VSS based campus design:

if the blades are interconnected between them this requires some attention.

Hope to help



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