How to verify the correct route is being used

If you have more than one default route and wants to make sure that traffic is flowing as expected via the right route, you can run a trace route from a machine in the local area network, this will indicate you the first hop that the traffic goes through.

 

Sample output:

C:\>tracert www.fortinet.com

Tracing route to www.fortinet.com [66.171.121.34]

over a maximum of 30 hops:

 

1 <1 ms <1 ms <1 ms 10.10.1.99

2 1 ms <1 ms <1 ms 172.20.120.2

3 3 ms 3 ms 3 ms static-209-87-254-221.storm.ca [209.87.254.221]

4 3 ms 3 ms 3 ms core-2-g0-2.storm.ca [209.87.239.129]

5 13 ms 13 ms 13 ms core-3-bdi1739.storm.ca [209.87.239.199]

6 12 ms 19 ms 11 ms v502.core1.tor1.he.net [216.66.41.113]

7 22 ms 22 ms 21 ms 100ge1-2.core1.nyc4.he.net [184.105.80.9]

8 84 ms 84 ms 84 ms ny-paix-gni.twgate.net [198.32.118.41]

9 82 ms 84 ms 82 ms 217-228-160-203.TWGATE-IP.twgate.net [203.160.22

8.217]

10 82 ms 81 ms 82 ms 229-228-160-203.TWGATE-IP.twgate.net [203.160.22

8.229]

11 82 ms 82 ms 82 ms 203.78.181.2

12 84 ms 83 ms 83 ms 203.78.186.70

13 84 ms * 85 ms 66.171.127.177

14 84 ms 84 ms 84 ms fortinet.com [66.171.121.34]

15 84 ms 84 ms 83 ms fortinet.com [66.171.121.34] Trace complete.

In this scenario, the first hop contains the IP address 10.10.1.99, which is the internal interface of the FortiGate. The second hop contains the IP address 172.20.120.2, to which the wan1 interface of the FortiGate is connected, so we can conclude that the route via wan1 interface is being used for this traffic.

 

Also debug the packet flow in the CLI shows the route taken for each session.

 

Sample output:

id=20085 trace_id=319 func=vf_ip4_route_input line=1597 msg=”find a route: gw-172.20.120.2 via wan1″

For more information on debuging the packet flow, see How to debug the packet flow.