BGP-AS Number

[Joe Lee]

Working with the customer, all their sites are connected to the service provider via eBGP. One of the sites (see diagram router C) will be relocated, they want to keep the same AS nubmer in the new facility (see the diagram router D), During the transition, our goal is to not affect any business in the old facility (router C) and we are able to access to the new facility from the other locations. (They don't need to access from router C to D). Not sure the allow-in or local-as commands work for this situation. Please advise.

Regards,

Joe

[Mohamed Sobair]

Hello,

Acordination between the Customer and the ISP is required here, you just need to make router (C) runs on different AS by having local-as feature implemented on router-c.

Have the ISP Provider peers with AS (65005) for example which is router-c , and configure (Local-as) in router-C. In this Scenario, No changes are done on all branches, plus all branches would still prefer Router-D (AS 65004) for the normal coomunication since it has the shortest AS-Path. If they require communication to the Old site (Router-C), then you would Prepend AS-Path on the New Location (Router-D) so that Router-C becomes more prefered for AS 65004.

Regards,

Mohamed

[Joe Lee]

Hi Mohamed, do you think it will worked to run "allowas-in" on the router C and D? My concern is not to impact any business in the old facility? thanks.

[Mohamed Sobair]

Joe,

You dont require (allow-as in) Here in this Scenario.

If you believe a small change and coordination with your ISP is an issue for you for what I have proposed earlier, then Your ONLY option else is to run IBGP between site C and D respectively.

Just leave Site - C with AS 64004 and Site D with AS 64004 and run IBGP between them over the ISP cloud. In this situation a communication between all Sites including Site-C and D take place without the need of any changes or impact and coordination with your ISP.

Let me know if you have any other question,

Regards,

Mohamed