VSS data path?

[anowell]

Simple question...

I'm trying to understand the data path when you have VSS configured.  I have a remote switch that has two connections to a pair of 6500s that are running VSS.  If I was plugged into the remote switch, what connection would I use to get to the the 6500s?  Both?  How is this determined?

THANK YOU VERY MUCH!!!

[Leo Laohoo · Accepted solution]

The fastest way to identify which one is active and which one is on hot standby is by looking at the LED light on the supervisor card.  Hot standby unit has the "Status" LED on amber color.  

When you console into a standby unit, the prompt is also a give-away.

[Jon Marshall · Accepted solution]

Either connection could be used for traffic to and from devices connected to the remote switch.

With VSS one switch is active and one standby for the control plane but in terms of the forwarding plane both switches can forward the traffic.

Presumably the links from the remote switch are configured as an etherchannel to the VSS pair so it is the etherchannel load balancing method that determines which of the physical links to use.

Jon

[Joseph W. Doherty]

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Posting

From remote to the VSS pair the operation is the same as from remote to any other single device, where you have multiple connections, i.e. the remote device "decides" path.

From VSS pair to remote, VSS avoids transiting its VSS mate.  I.e. whether Etherchannel or L3, VSS will use its own link connected to the remote device.  (I.e. VSS doesn't load balance, you load balance to the VSS transit pair and it will maintain the same load balancing.)