[CentOS] High Availability using 2 sites -- yep, "propogation."

Sat Jan 7 21:19:26 UTC 2006
Lamar Owen <lowen at pari.edu>

On Thursday 05 January 2006 13:51, Les Mikesell wrote:
> BGP would normally be used to handle routing over multiple
> paths to a fixed location and would change in response to
> the route availability.  You can play tricks by shuffling
> a route to a completely new destination if a whole site fails
> but the minimum you could move would be a whole class
> C at a time, and some bad things will happen during the
> switch as different machines with the old IP's become visible.

I don't know; BGP4 could do this, even though it is not the smoothest 

However, let me correct one point.  On today's Internet, there is no such 
thing as a class C.  Now, as to whether prefixes longer than /24 will be 
propagated or not, well, more than likely you won't get a prefix longer 
than /20 propagated through most AS's BGP tables these days.  So 
route-flapping smaller CIDR blocks than /20 is futile unless you have good 
solid agreements with all the BGP-speaking AS's your traffic needs to 
traverse; that is, you'd need to make sure the AS's you care about propagate 
your prefixes in all their glory.  Man, that would fit right in on NANOG, no?

Gepgraphically diverse HA solutions are fascinating to me; getting a working 
CentOS solution that is architecture agnostic would be fantastic.
Lamar Owen
Director of Information Technology
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC  28772