- L3 access layer switches
- VLANs extended across two switches
The VLAN extension requirement usually spawns from a server NIC redundancy (teaming), or from the desire to have pooled systems on the same subnet, but with diverse upstream network hardware.
The deployment winds up looking something like this:
There's a full mesh of OSPF point-to-point links in the topology including an East-West access layer adjacency on VLAN 10, which rides the same L2 aggregate link as the access VLANs. Yesterday, I said "don't use SVIs for routing adjacency." I confess: I've done it myself. Lots.
But now I'm starting to wonder why I've done it.
If all VLANs are shared between the two access switches, then what benefit do I get from the adjacency on VLAN 10? I'm starting to think the answer might be "nothing." Maybe I should eliminate it.
We've already got Equal Cost Multi-Path to everything else in the network, and any traffic between access VLANs will always be locally routed (and then bridged across Po10 when necessary).
Is there a case to be made for keeping this link, or should I kill it off?