BGP, two routers, two ISP, preferred path inbound

[wilson_1234_2]

We have two ASR routers, with two different ISPs. Currently there is a Primary router inbound and outbound, the second router is backup to the Primary.

The config is pretty much identical on the two routers. We have a Public address block we are advertising from both routers.

They have HSRP configured, which the priority on that config, selects the Primary router for outbound traffic.

What I don't see, is how the inbound path is always preferring the Primary router and ISP. There is nothing in the config to prioritize one ISP over the other, no metrics set, no AS path prepending.

We are replacing the second ISP with a new carrier and much higher BW and I need to determine how the Primary ISP is always preferred.

Is it possible the original engineer worked out something with the two ISPs?

Anyone have any thoughts on this?

[Georg Pauwen]

Hello,

it is definitely possible that the ISP configured something on their end so that one route is preferred.If you do a 'show ip bgp neighbor x.x.x.x' for both neighbors, there should be an indication in the output of what is configured. Can you post that output from both neighbors ?

That said, with AS-PATH prepending on your end, you should influence the inbound path...