Routed Access vs VSS distribution with MEC

Hi All,

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I am looking at a design for a new campus network and a question has been raised of whether to design it using a virtual distribution layer (with VSS or Virtual Stackwise) with Multichassis Etherchannels to the access layer, or use L3 routed access. I have been asked to look at this as I have been told that routed access provides faster convergence but I'm not sure if this based on old info.

I know that one of the common constraints with using routed access is the inability to stretch VLANs between access layers and I have been told that this is 100% not a requirement for this network so routed access may be a viable solution. What I'm struggling to understand is the benefits over routed access vs the more common design of a virtual distribution and MEC to the access layer.

With both solutions, spanning-tree is not involved in convergence and both can provide quick convergence in the event of a link failure. Routed access uses ECMP and the L2 design uses the inherent capabilities of multichassis etherchannel. I've also seen some references that hardware based etherchannel convergence is faster than 100ms. As a result, I dont see convergence as the deciding factor between these two designs.

I can also see that routed access will limit the broadcast domains to the access layer and not to the distribution layer but again is this really a concern? Maybe this is a consideration if the access layer had a large number of ports etc?

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Any pointers would be really appreciated.

Thank you

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