[j-nsp] Migration from IGP to e-BGP

[Justin M. Streiner]

On Fri, 28 Dec 2012, tim tiriche wrote:

> We have multi area OSPF and would like to migrate the multi area to
> private ASN BGP islands.

How are you defining an 'island'?

> Main ASN:1234
>
> Problem:
>
> In the current OSPF areas there is an e-BGP Peering and Transit with customer.
> After migration, how can i ensure that customer peer using the Main
> ASN:1234 and transport it over the core?

"Peering" and "Transit" mean two different things to a number of people 
who read this mailing list.  I'm guessing you mean one or the other (most 
likely transit)?

If the customers speak eBGP with you today, and your end of the session is 
in AS1234, then the customer's traffic will transit AS1234, depending on 
what you do with the traffic while it's on your network.  If I'm
understanding your intentions correctly, what do you hope to gain, or what
problem are you trying to solve by creating 'private ASN BGP islands'?

If the issue is reducing the number of IBGP sessions on your backbone, 
have a look at route reflectors and BGP confederations.

> How have others done it?

In my past life, we spoke eBGP with our downstream customers.  Either the 
customers had their own public ASN, or we used another public ASN that we 
had available at the time.  Private ASNs were used in a few corner cases. 
The latter two approaches impose limitations that might not be acceptable 
for some customers.  YMMV.

jms

> Loops, local-as? Would independent domain help?
>
> Looking for suggestions.
>
> Sincerely,
> -Tim
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