Collapsed core network design

[Marc Bouchard]

I am a consultant, currently a CCNA studying for the CCNP, and I have been mandated to design the network infrastructure for the corporate head office of a mid sized company.

My design is based on a collapsed core network, with 2 x 4900M Switches as the core/distribution and a bunch of 2960S switches for each floor of the building.

While reading the CCNP book, I noticed I had a design 'flaw'...  Like the partial diagram below (this is not the actual design), I was planning on linking the two 4900M with a layer 2 etherchannel, and using 1 MST region with 2 instances to split the VLANs between the two core switches.

The CCNP curriculum recommends using a Layer 3 link between the core switches. I'm not sure what the benefit of doing so would or the drawback of using Layer 2 is? Any input would be more than appreciated...

Thanks,

Marc

[gosselic · Accepted solution]

With today's layer 3 switches it is easy to have a L3 Core/Distribution working at the speed of LAN ports. A L3 Core limits the need for spanning-tree, broadcast domains and the potential for network loops.

[Marc Bouchard]

I understand that it reduces the chances of loops, but spanning tree is still required/running no? I'm going to lab this today and come back with observations or questions if I have any

Thanks for your time,

Marc