BGP Design Question

[brian0656]

The border routers in my network run EIGRP and BGP. All other routers run EIGRP only. There are 2 WAN connections to the same ISP.

The config on the border routers look something like this:

router BGP 100

redistribute EIGRP 100

neighbor 1.1.1.1 remote-as 200

There are no dynamic default routes to the internal routers and no iBGP with the other border router.

What am I missing that will provide fault tolerance other than having multiple static default routes?

Do I need to have BGP running on all routers in my AS?

My organization has networked their routers this way for years and I think that the routing can be done in a smarter way.

Thank you to anyone who replies.

Brian

[rawatmohinder]

Hi Brian,

I am not able to get u properly. it will be easy if u send the show running-config of your edge routers.

Thanks

Mahi

[spalislam]

Hi Brian,

First I am not sure when you say two WAN connections, do you meen two different paths,interfaces to the same ISP, or two different routers to the same ISP. Most likely second one.

If so, in reality you have two choices.

1. No need for BGP. Use static routes and redistribute them to EIGRP. However, in this case, you could blackhole the traffic if remote end interface is up, but it itself is blackholing it due to its IBGP sessions within ISP going down.

2. Run EBGP, but since it is the same ISP, there is no need to run full BGP table. Have them advertise you only default route. Then take that route and readvertise it into EIGRP, from both routers. Additionally, have your ISP do some policy modification to assure they don't blackhole you. In this case as long as BGP is up, and redistribution to EIGRP is good, EIGRP will pick better cost to each of ASBR's 0/0 route. In the case one of the BGP peerings goes down, 0/0 will be removed from the database.

However, the best scenario would be if you could do your EBGP peering with two different ISPs, preferably ones who have different ISPs themself, so you would have a better change of redundancy.

I hope this helps.

Regards,

Senad