BGP Path Selection (local pref/as_path)

[rmessina]

I have two WAN connections (OC3 and DS3) in two separate routers.  Both connections are to the same private MPLS cloud.  My company would like to force all traffic over the OC3, and use the DS3 only in the event that the OC3 fails.  I've successfully tested using local preference to influence outbound traffic, and using AS_Path to influence inbound traffic.  This was tested in a lab environment.  I know there are multiple solutions to this problem, but I wanted to make sure that the local pref/as_path was an efficient choice.  Any reccomendations are greatly appreciated. 

[Giuseppe Larosa]

Hello Randy,

the solution that you have tested works.

if both eBGP sessions are to same AS number you can influence inbound traffic by using MED ( BGP metric), the lowest MED is preferred but default value is 0.

in the route-maps instead of setting as path prepending you could set metric using set metric

You can also set both AS path prepending and MED

Hope to  help

Giuseppe

[rmessina]

Thanks for the reply Giuseppe.  I have found that in the lab the solution above works until I fail the primary BGP connection.  Once it is restored, the primary never takes back over.  It's like the route-map isn't being reapplied.  The command show ip bgp no longer lists the primary connection with correct local preference. 

[rmessina]

Note: I have to manually clear ip bgp * to get everything back to working order after a failure.

[rmessina]

nevermind... something i did fixed it... oh well, I guess that's how it goes sometimes.