BGP default route and weight

[pthaynes]

I have connections to two different ISPs and would like to configure OUTGOING traffic so that it will go to secondary ISP for traffic to their direct customers and the main ISP for all the other traffic. In the event of a failure I would like traffic to travel via the secondary ISP. The problem I have is that one of the clients that connect to us requires us to advertise out all domestic BGP routes plus a default route.

This means I need to get all the domestic routes from the main ISP plus a default route. From the secondary ISP I need routes to all of their customers plus the default route. Is there an easy way to set the weight on all routes from one BGP neighbour with a high weight for all routes EXCEPT for the default route?

[frenzeus]

Hi,

I assume you have one router connected to both Primary & Sec ISP? If all traffic will flow through this router, u can specify a route-map on the incoming direction from sec. isp, set a higher weight for the specific sec. isp direct customers prefixes advertised to ur router.

But rarely it will be only 1 router. So what u can also do is to specifically set the prefixes from sec. isp direct customers with a higher local pref, that will take care of the preferred router to use to reach your secondary isp direct customers from within your own AS.

ie.

assume 192.168.1.0/24 & 192.168.2.0/24 is sec. isp direct customer prefix

ip prefix-list isp2-1 seq 5 permit 192.168.1.0/24

ip prefix-list isp2-1 seq 10 permit 192.168.2.0/24

route-map isp2 permit 10

match ip address prefix-list isp2-1

set weight 40000

route-map isp2 permit 20

neighbor x.x.x.x route-map isp2 in

You can also replace weight with local preference. That's what i think. Correct me if i'm wrong.

[pthaynes]

I'm OK with using a route-map to set the weight. What I would like is to be able to select just the default route from the secondary ISP and set the weight on it to be lower. What sort of Access-list / match statement can I use to match up with only the default route?

[frenzeus · Accepted solution]

If your intend is to just modify the default prefix advertised from the sec. isp, u can use a prefix-list to match it:

ip prefix-list isp2 seq 5 permit 0.0.0.0/0

route-map isp2 permit 10

match ip address prefix-list isp2

set weight 20000

neighbor 1.1.1.1 route-map isp2 in

i'm assuming u have no other route-maps attached in the same direction for sec.isp peer link.

Hope this helps.