Figuring out the Exit Interface of an OMP Route in cEdges by Routing Tables

Let's start from looking into the configured VRF numbers through CLI by command show vrf

(click on the images to view in full size)

As we can see the; VRF 1 is configured in this router. Other 2 VRFs are default configured VRFs. So this VRF 1 is the only Service VPN we can see here which the OMP routes are learned.

Let's check the routing table of VPN 1 by following command,

show ip route vrf 1

In OMP (Overlay Management Protocol), there is this concept called TLOC (Transport Locator) to identify the hop and transport which the traffic should be forwarded to.

TLOC contains of 3 components;

1. TLOC IP (System IP of the Hop)

2. Color (the transport eg:- biz-internet, MPLS, etc)

3. Encapsulation Method

Let's analyze a specific route, 192.168.11.0/24, the next-hop is 10.1.1.111 which is actually the TLOC IP (System IP of the WAN edge router) which is not need to be routed from other WAN edges, just like a OSPF router id. So let's find the public IPs of the TLOC transports by the following command..

show sdwan omp tlocs | b 10.1.1.111

So to reach the TLOC IP of 10.1.1.111, there are 2 public IPs 172.16.1.1 and 10.10.11.1

Now let's check how those IPs can be reached through the default VRF which is actually the underlay VPN (VPN 0) of SD-WAN domain.

show ip route

So as you can see from the above output, the traffic will be load balanced between GE 1 and GE 2 interfaces.  

All above was done to resolve next hop IP and exit interface by examining routing tables. Following command will give you the same information at once and hope now you know how it is derived and that is nothing but the forwarding table.

show sdwan ip fib

Red box shows the next hop addresses of the route in the Service VPN (Overlay VPN).

To find the physical exit interface; 

show ip cef

Note that since AAR (App Aware Routing) in SD-WAN is defining the traffic forwarding in case it is configured. You can simulate to visualize the actual traffic flow in vManage GUI interface.