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Community Member

BGP Hardware

I'm in the process of setting up a redundant internet connection with two ISPs. I have two routers, each one connected to an ISP. Each router only has two interfaces. Is this going to work well? I'm thinking that there might be a bunch of issues with this configuration.

I'm wondering if it would be a better solution to

-add an additional interface to each router

-connect each router to each ISP

-use hrsp to failover

Comments or ideas?



Community Member

Re: BGP Hardware

We've got what sounds like a similar situation. We opted to do one ISP per router and use iBGP between the two routers to load balance and failover at the ISP level.

Advantages for one ISP per router:


*Second router is actively used (how do you know the router is still good if it's not being used?)

Advantages for two ISP per router:

*Slight improvement in the path latency if one ISP dropped

*Cleaner data flow (one hop as opposed to two)

We chose option one. I'd be interested in seeing what other people think.


Community Member

Re: BGP Hardware

Are you taking full routes from both ISPs? Right now, I'm only taking a default from each, and using statics to control routing.


Community Member

Re: BGP Hardware

Yes, we are taking full routes from both. The problem I saw with using default routing is that you have no way of distinguishing if either ISP is having problems, and say drops a few routes to various parts of the Internet. With full routes, you should receive notification of that kind of problem (withdrawn routes) and start using the other ISP in that case.

Hall of Fame Super Gold

Re: BGP Hardware

Hi, in the internet is a very rare case that a reputable ISP cannot reach some destinations. Even if a direct link to that destination fails, traffic is rerouted by some other path.

Because of this default routes also work well in a customer<->ISP BGP link.

Of course if you have the appropriate router and circuits to use full tables, that is OK as well.


Re: BGP Hardware

Several ways to set this up, and it appears you are on the right track.

some of this comes down to how complicated you want the config to be.

You can use HSRP, as you suggested.

You can us iBGP, probably the best option as someone else pointed out.

alot of this comes down to the type of network you want to have, or contracted to have.

some locations I have worked with had 2 T-1's separate routers but one of the T's was only for failover so it would not be used until something happen to the other T-1. This would change what you would want to do.

so whatever your design there may be something more specific you would want to run. However, sounds like you would want to do iBGP or PfR routing.


I have not done this yet, but do have a need in the neer future and this seems to be a pretty slick set-up.

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