@bhubert wrote:
Version 6.5.3.4
controller IP is the loopback
loopback IP is same subnet as VLAN 254
controllers also have IP in VLAN 129
Airwave is in VLAN 129
TCP packets between AirWave to loopback and/or interface IP in 254 exhibits same behavior - asymmetric route
To ‘fix’ this we added a route to the controller that would force traffic from both controllers to use VLAN254’s gateway for the AirWave host IP in VLAN129. We removed asymmetric routing support and we tested. It worked!
This behavior is correct, and here's why...
The controller has more than just the default route in the routing table. If you run "show ip route" from the CLI, you'll see the default route of last resort, in addition to any connected interfaces. The only interface that will not show a connected route is the loopback interface, since it is assumed to have a /32.
When traffic arrives to the controller's mgmt interface (the loopback interface), the controller will consult the routing table for determining which interface the response should go out of. As Mark mentioned, connected interfaces have a higher preference than static routes, in addition to being more specific. In this case, the connected interface on VLAN 129 is the shortest path, so it gets used.
Your fix works because it provides a more specific route. Rather than a subnet route pointing out VLAN 129, you provided a host specific route (/32) out the other VLAN.