I am wondering if there is any specific requirement for two routers to form ISIS adjacency over a switched ethernet network ? In other words, when they are not directly connected.
I have two ASR9K routers - R1 and R2 - connected directly over a BE interface of two 10G interfaces:
R1 (be12[te0/0/0/1, te0/0/0/2]) ----- (be21[te0/0/0/1, te0/0/0/2]) R2
BFD and ISIS is configured and running properly on both of them. So far so good.
For some testing purposes I am replacing the directly connected Te interfaces of the bundle with a single interface, that is connecting R1 and R2 over a vlan of a switched infra (N9K switches)., like this:
R1 (be12[gi0/0/0/0]) -----(access port vlan 10)N9k1 ---N9k2---N9k3---N9k4(access port vlan 10)--- (be21[gi0/0/0/0]) R2
This time LACP over the bundle is turned off (mode on). No other changes in either BFD or ISIS.
BFD session is up, ping works correctly, but ISIS adjacency is not formed, ISIS neighbors are not visible. Turning on ISIS debugging I can see "0 neighbors" displayed for hello messages.
So my question is : should this be working or not ? If not, why not, or what is missing ? To my understanding, although ISIS is not an IP protocol but CLNS, which runs over ethernet and hence the ethernet switches should simply forward this traffic. Or not ?
It may worth mentioning, that on the Nexus switches isis feature is disabled. Can this be an issue ? They should not play any role in ISIS routing, just forwarding traffic.
