[c-nsp] BGP Considerations isolated PoP

[Joe Provo]

On Wed, Sep 14, 2005 at 05:50:48PM +0100, Mark Tohill wrote:
[snip]
> We have our public AS announcing our /16 network over 2 PoP's to single
> upstream providers two adjacent PoP's. iBGP configured as it should be.
> 
> What are the considerations if a third PoP were to be implemented, yet
> this would, for the time being, be essentially isolated from remainder
> of our network?

Depending on what you're doing, and for how long, there are multiple
viable approaches.

If it is going to be single-homed, consider just getting PA space
and have a renumbering plan in-hand for when you stitch it together.
If the isolation is going to be short term, this would allow you 
to avoid complexity right out of the gate. Just be sure you can 
announce the PA slice out of your ASN when you are in the stitching-
together transition period.  Don't ignore the simple solution just
because it isn't "sexy". 

If the third site is going to have decent redundant connectivity, 
put some tunnels up so the logical topology follows what it will 
be when you stitch it together & appears consistant.  Then you'd 
also be safe using your ASN in the island.  Default + conditional 
announcement for a decently-sized slice of your /16 would provide 
good belt-n-suspenders.

Cheers,

Joe
 
--
Joe Provo                                            Voice  617.670.2904
Senior Manager, Internet Planning & Design           Fax    617.670.2920
Network Engineering, RCN                             <joe.provo at rcn.com>