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

[tim tiriche]

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

How have others done it?

Loops, local-as? Would independent domain help?

Looking for suggestions.

Sincerely,
-Tim