Friday, June 12, 2020

Layer 3 Multi-Chassis EtherChannel (MEC)

For anyone that didn’t read my last post, the company I recently started working for is undergoing a network refresh. Geographically, it's just a single but extremely large campus LAN with zero branch offices. The current LAN architecture is a full cisco shop, classic 3 tier core, distribution, access layer hierarchical model. The core consists of two VSS linked 6509's where all routing is done, these aren't being touched. The distribution layer in each building/area consists of a single old 3560 which currently has two 1gig fibre uplinks back to each core VSS 6509. All these distribution switches are in scope for this refresh. Layer 2 is currently being spanned all the way up to the core. A friend outside of work has convinced me to bring routing down into the distribution layer.. if not to the access layer even, to protect the core VSS 6509 pair from any broadcast storms or layer 2 issues that could magically happen downstream in the access layer.

From my last post I mentioned I'm planning to put two stacked units to act as the new distribution layer switch for each distribution area of the campus. I've decided I want a Layer 3 link between the core and distribution layer, but I also want resilience, so what I wondered was this - can I run a Layer 3 port channel from the core VSS pair (one interface from each VSS 6509 unit) down to a Layer 3 port channel (cross stack) on a distribution layer stack? Will this work? Picture here: https://imgur.com/GLZCAIC

Anyone done anything like this? or am I just talking rubbish and this won't work/stupid.



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