[c-nsp] design ? - two POPs, same AS or different?

Roldan, Brad broldan at covad.com
Fri Aug 18 19:05:50 EDT 2006


Hi Matthew,

It is possible to have two POPs with the same ASN, although purists will
argue that this violates some fundamental unspoken design rule. If you
plan to also advertise the aggregate /20, you'll need to be careful
about how you inject the route in your local tables. The Internet at
large should be able to find your /22s in Europe and San Jose with no
problems. Traffic at your POPs advertising the /20 will likely go to
null0 if you just use the "aggregate-address" command. Without seeing
your actual configs, I'm just guessing.

At the location(s) where you would want to advertise the /20, one
possible solution would be something like...

router bgp <your ASN>
 aggregate-address 10.10.0.0 255.255.240.0
!
! Create a covering route, or a everything will go to Null0 
ip route 10.10.0.0 255.255.240.0 <eBGP neighbor next hop IP>
!


The solution has some drawbacks, but gets the job done.

Regards,

Brad
-- 
Covad Communications 
2510 Zanker Road 
San Jose, CA 95131 


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of matthew zeier
Sent: Thursday, August 17, 2006 10:42 PM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] design ? - two POPs, same AS or different?



This is a design question and I'm not sure the "best" way to solve this
- 
looking for suggestions.

I currently have a site in San Jose announcing a /22 out of my larger
/20 
behind a particular ASN.  In a couple months I'll be opening a second
site 
somewhere in Europe and announcing another /22.

I won't have any physical connection between each site but will need
each site 
to talk to each other.

Would I be better off getting a second ASN, putting up GRE tunnels and
peering 
or use something like allowas-in?

And to add to the complexity, at some point in the future I'll be
anycast'ing 
a portion of that /20 out of each site.

Thanks.

- mz
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