[c-nsp] Conditional BGP

[Jay Hennigan]

Hank Nussbacher wrote:
> At 09:47 PM 18-10-08 +0500, Masood Ahmad Shah wrote:
> 
> I am curious if anyone else uses conditional BGP as a poor man's DRP?
> 
> Suppose you have site A with 192.168.1.0/24.  The site is connected to 2 
> upstream ISPs and they have a number of servers at site A.  They now 
> create a DRP site (site B), which is also connected to 2 upstream ISPs 
> and they create a mirror copy of those servers from site A over at site 
> B and assign them the *exact* same IP addresses as at site A.  They have 
> the router at site B do conditional BGP, checking to see if it sees 
> 192.168.1.0/24 from the Internet.  As soon as it disappears (site A is 
> gone), site B starts announcing 192.168.1.0/24 to the Internet and all 
> the DRP servers at site B are suddenly active.  Ignoring the syncing of 
> the servers from site B to site A, what is the downside of such a "poor 
> mans' DRP solution?

It has possibilities, but consider:

How do you get it to fail back to site A when site A is restored?

How do you protect against a temporary or transient failure?

What mechanism is in place to prevent both sites from being live at the 
same time?



I think there should be some form of out-of-band communication between 
the two sites to keep things in sync.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
Impulse Internet Service  -  http://www.impulse.net/
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