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BGP ASN number change

                   My ISP mistakenly gave me a duplicate ASN for one of my sites.  So 2 sites have the same ASN - lets say 45009.  One site should be 45010 and the other 45009.  THe ISP has assigned me the new number but wants to schedule a "cutover".  I thought I would just make the change on my router and then do a #clear ip bgp *

Although it just occurred to me that I'd probably lose connectivity to the router as I'll be doing this remotely.  I could probably do a reload in 5 command or have someone on site.


Everyone's tags (3)

Re: BGP ASN number change


The ISP will need to change their neighbor statement to you also, which is why they may want to do a cut. Even if you changed your end, they'll need to change the AS that they're peering with. Until they do that, your peering wouldn't come up.

As far as changing your config, you wouldn't be able to change this remotely unless you have a backup circuit into the site. That being said, you can change your startup config. What I would do is to tftp their current running config, modify it to the new asn, and then tftp it back to the startup config. Then reload the router. The router will come up with the new config, but you'll still probably want to have someone onsite in case something doesn't work as expected.



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HTH, John *** Please rate all useful posts ***

Re: BGP ASN number change


It is possible to use the existing AS and use the proper AS also but only as an interim, it is usually suggested to change to the proper AS when applicable.

router bgp 45009

neigbour remote-AS 1234

neigbour local-as 45010 no-prepend replace-as



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BGP ASN number change


what about configuring a default route on the remote router pointing to the provider router and connecting to the remote router WAN IP address from your PC?

The WAN subnet should be advertised by the provider router, shouldn't it?

So you should be able to keep your connection to the router even when the BGP peering is down, shouldn't you?

And to reconfigure the BGP AS number without any problem except of the remote LAN losing the conectivity for a while?

Best regards,


Re: BGP ASN number change

When I have been in situations like this I've used EEM applets.

Configure the applet to watch for the Syslog message that the neighbor went down and then to issue the proper commands to reconfigure the BGP configuration

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