OSPF between Spine Routers over a FabricPath VLAN

[jomihuertas]

Hi guys,

I have a Fabirc Path topology with 4 Nexus 6000. I need to establish OSPF adjacencies between these 4 Nexus using a FabricPath VLAN. I've done it, and apparently it's working, but when I have attached a new router to this network and I have configured it with OSPF to participate in the same domain as the Nexus, I have noticed some "weird" connectiviy problems.

The ASR is connected to two of the Nexu 6000 through vPC+, and they establish OSPF adjacencies (the ASR and the two Nexus). Then I have a fabric path VLAN for establishing OSPF adjacencies between the four Nexus (one of them becomes DR, another becomes BDR, and two of them becomes DROther).

What I have seen is that ASR learns through OSPF the IPs connected to the Nexus (let's say, Loopbacks) and all Nexus learn the IP of ASR's loopback. But when I ping Nexus Loopback from ASR Loopback, some packets are missed. Depending which Loopback destination I'm using, the ping is ok or is dead.

Can anyone tell me if this architecture is not supported (having OSPF adjacencies over a FabricPath VLAN) and why I'm having those connectivity issues?

[metal_icer]

Hello, jomihuertas!

The strange behavior when using OSPF over fabricpath is most probably caused because of the way FP deals with Multicast Trees. Especially with the default behavior of the Multicast ECMP. I had a scenario in one vrf OSPF on SVI FP spines was working ok with connected ASA in one b-cast domain, but the same story in another vrf, some of the spines didn't receive any OSPF hello messages. Adding the VLAN in quesion on all spines in the FP domain resolved the issue.

Hristo

[Kristiyan Mladenov]

Have you checked if the Control Plane Policing on the Nexus has kicked in? It is somewhat nasty for the unaware network admin.