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I have a possible disaster recovery scenario, use a production server with public IP from AT&T, the disaster recovery server should have the same public IP but with a different ISP (Time Warner or Verizon).

Can this be accomplished and if so what do I need to do or have done at the ISP level?

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2 Answers 2

No, this cannot be done. At best, there would be a routing conflict and some people would go to the main server and some people would go to the recovery server.

Either way, if AT&T owns a particular public IP, nobody else is allowed to broadcast it as theirs, so even if your main server goes down and "stops using" the IP, another ISP cannot claim the IP and give it to your recovery server.

You need to use DNS to handle this kind of failover, where your DNS entries have a low TTL and update when the main server goes down to change to the recovery server's IP.

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If you own a particular public IP range, though, you would be to "broadcast" it from multiple locations. Although I seem to remember one needs at least a /24, which wouldn't be easy to get even for a business. –  grawity Oct 11 '12 at 19:59
@grawity That is multiple routes pointing to one location, which is different from multiple routes pointing to multiple, different locations. –  Darth Android Oct 11 '12 at 20:22

It's not impossible but it's pretty complicated. You want to investigate multi-homing. Here's a long presentation I found discussing multi-homing you might want to take a look at, but I think it's probably too complicated for an answer here.

Check out http://www.freedman.net/multi.ppt

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