For┬áa few┬áyears, Cisco have been positioning the Cisco Catalyst 6500 VSS within the data centre. Whilst VSS does indeed have many positive benefits (for VSS think about stacking a pair of 6500s like you do with a pair of 3750s, it’s the same concept) – including allowing you to port channel your edge switches into both “sides” of the VSS. Spanning Tree is no longer┬ámandatory – as the edge switches are connected to a single logical switch and there are no loops.

At layer 3 again, things are simpler. No more HSRP/VRRP – as the two physical 6500s present themselves as a single logical device.

However, one of the major issues has always been the lack of support for dual supervisors within a single chassis. Initial and subsequent releases of VSS only supported a maxmium of one supervisor per chassis. Failure of that supervisor would take the whole chassis down; whilst the VSS would stay up, any device that was only attached to the failing side would lose network connectivity.

The good news: it seems that in the latest IOS version for the 6500 , this has been addressed:

Quad-Supervisor Uplink Forwarding on In-chassis Standby Supervisor Engines

As a personal opinion, I think a feature rename to “Dual Supervisor Redundancy” is required, but that’s just me! We’re in the process of testing this new feature, and we’ll let you know how we get on.