Asymmetrical Routing

[dvino821]

Hello,

While doing some testing in the lab (NSX 6.1.1 and 6.1.4), I have noticed that ESGs (with dynamic routing enabled, OSPF in this case) seem seem to drop packets, if they:

- Receive a packet from a source address, on an interface, that differs from the interface, that the route in the routing table specifies, that matches that source address.

I have not seen this documented anywhere. Any feedback would be helpful.

Thanks,

Dave

[DaleCoghlan · Accepted solution]

The NSX ESG is implementing Unicast Reverse Path Forwarding (uRPF).

You will normally see this when running a pair of Edges with ECMP and you try to ping an interface on the "other side" of one of the Edges from where your packet originally come from. If your packet didn't traverse the same Edge it is pinging it will generally be dropped by uRPF as it will show the route back to the source going out a different interface to the interface the packet was received on.

Dale

[dvino821]

Thanks!

I just heard the same from support today.

Doesn't seem to be documented anyway though.