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Internet redundancy between corporate sites

I have two C1720 routers whose Ethernet interfaces are on separate subnets, separated by a PIX FW. One router connects to the Internet, the other connects to a P2P circuit connecting two sites. Each site is configured similarly with two routers (one Internet and one P2P). I would like to be able to redirect Internet traffic from either site across the P2P circuit as a backup in the event of a Internet (serial) link failure.

I'm not sure if this can be done. Or if so, how.


Re: Internet redundancy between corporate sites

There are several approaches that may work for you, depending upon your exact needs and whether or not you are also providing services to clients on the Internet. There is a brief discussion of various multihoming options, with and without using BGP, in one of the white papers on my web site.

At worst, you will need to get an ASN and start running BGP with both your ISPs. At best, you may be able to play games with NAT and not need to spend any money on an ASN or bother your ISPs. But a lot depends upon whether or not you can automatically detect when your link to an ISP goes down (or the ISP goes down). You may find it necessary to get a toy SOHO box which uses ping and/or http rather than a real routing protocol to detect ISP problems.

Good luck and have fun!

Vincent C Jones

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