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BGP with 2 ISP's

I have two 1841s each with a T1 going to two separate ISPs. The ethernet interfaces on both routers are in the same subnet. I will be using BGP

The requirements are to:

1.)Have redundant ISP’s

2.)Have redundant T1’s

3.)Have redundant Routers

4.)Utilize both connections

Is this possible using BGP alone?


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Re: BGP with 2 ISP's


You certainly can use redundant ISPs with BGP. You certainly can have redundant T1s with BGP. You certainly can have redundant routers with BGP (and will need to run IBGP between your two routers as well as EBGP between your routers and the ISP routers).

Whether you will really utilize both connections depends a bit on how you configure BGP (and perhaps on whether you would consider having one as a backup path and one as primary would constitute utilizing both connections). It is fairly simple to configure BGP to use both connections at the same time for outbound traffic (which you control) and can be a bit tricky to get inbound traffic on the T1s (from the ISP to you) since you do not have direct control over how the ISPs route to you.



Re: BGP with 2 ISP's


yes this is possible. Have a look at

"Load Sharing with BGP in Single and Multihomed Environments: Sample Configurations"

The configuration examples should give you a guideline on how to setup your internet access. Also make sure to have proper filters in place to prevent becoming a transit AS, accept private IP networks and the like.

Hope this helps



Re: BGP with 2 ISP's

Are the two routers sitting on a LAN, to which they are providing Internet Access?. If so, you do not have router redundancy. If the router that is the default gateway of the LAN dies, connection to the Internet will be broken. You will need to use something like HSRP or GLBP in this situation.

If the ethernet interfaces of the two routers are connected to core network, and you have an IGP running, then, you should have router redundancy.

I believe other requirements are well taken care of by BGP

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