Dual ISP Circuit Priority

[davidreyes13]

Looking for some advice on how set one interface as the primary traffic passing interface over another without shutting down one of the interfaces or associated tunnels. We currently have dual ISP circuits using 2 tunnels to reach our corporate environment, but we would like to set a metric that will "choose" one circuit over the other. We tried a delay statement on the associated tunnel interface and/or physical interface but we are still seeing traffic go through both circuits. 

Any ideas? 

[a.alekseev]

It depends on the configuration

[chrihussey]

Are you running a routing protocol across the tunnels?

[davidreyes13]

I believe EIGRP is used. 

[Joseph W. Doherty]

You're sure there's data traffic on secondary? Reason I ask, even if you've insured the secondary has a higher path metric, if you're running a dynamic protocol, routing updates and "hellos" are still going to go across that link. (Also there's some "optional" stuff that can cross a tunnel, like keep alives and/or CDP.) Some routing protocols do have features, for "on-demand" links which can mitigate their usual "overhead" traffic.

[davidreyes13]

Yes. We will see that one circuit is doing all the receiving and the other is doing all the talking. We monitor traffic on the circuits and we see bandwidth utilization peaking on a circuit that has a delay value on it. 

[chrihussey]

It sounds like you have asymmetrical routing going on. To properly influence routing the metrics, in this case the delay, need to be configured on both sides of the tunnels. Is this the case?

[Georg Pauwen]

On a side note, if you are using EIGRP, delay should be sufficient. Check the output of 'show ip eigrp topoloy' to verify the number of successors for a given prefix. In the example below, the delay on interface GigabitEthernet0/1 has been increased, and the number of successors drops from 2 to 1:

R1#sh ip eigrp topology

P 4.4.4.4/32, 2 successors, FD is 131072
via 192.168.12.2 (131072/130816), GigabitEthernet0/0
via 192.168.13.3 (131072/130816), GigabitEthernet0/1

R1#sh ip eigrp topology

P 4.4.4.4/32, 1 successors, FD is 131072
via 192.168.12.2 (131072/130816), GigabitEthernet0/0
via 192.168.13.3 (158976/130816), GigabitEthernet0/1