Path preference in FTD

[uditsaxena]

I am receiving two default route from OSPF with same metric. All the routes in Area 0. It is preferring one router why ? 

[Marvin Rhoads]

Are they coming in with the same metric?

[uditsaxena]

Yes, they are coming with same metric

[Marvin Rhoads]

That's interesting.

Are both routes in the table but the observed traffic prefers one over the other? If that's the case, the perhaps FTD is using per-destination load balancing algorithm as opposed to per-packet. I wasn't able to locate documentation stating which is the case.

[uditsaxena]

Two default routes are coming with two different interfaces with same metric, this we can see by #show ospf rib but route is installed only through one interface (see the image for ref). But in case of router, if two default routes are coming with same metric from two different interfaces, it will do the load balancing. But FTD is not doing so. Just wanted to know how FTD is choosing path.

[Marvin Rhoads]

According to the documentation, it should dynamically load balance the traffic across both paths.

Do you have a support contract? If so, I would recommend opening a TAC case for further investigation.

[uditsaxena]

Hi Marvin,

I opened a TAC case they say FTD does not load balance the traffic if it is receiving route with the same metric from two different interfaces as router do. It will install only one route and that will be based on the oldest path.

[Marvin Rhoads]

Thanks for the update. That's concerning news. I would argue that it's not really doing ECMP at all - contrary to the product documentation. I will be sure to provide this feedback to Cisco!