04-29-2010 08:48 AM - edited 03-04-2019 08:19 AM
I have a client who's company was split in half. One half is keeping their IP ranges and ASN, and the other half must be reconfigured with a new
ASN and IP block. We have obtained the new ASN and block from ARIN and have peering agreements in place. The routers are still advertising the old ASN, and we need to make a cutover. What is the most efficient way to cut to the new IPs and ASN with the minimum amount of downtime?
I can post configs if needed.
thanks,
Paul
04-29-2010 09:50 AM
Hi Paul,
I have not done it but how about using the BGP 'local-as' feature. Have the neighbor AS peer with your new AS as true ebgp connection with ' local-as
I will let someone else comment on that as well and its been a while and I need to brush up my things again.
regards,
04-30-2010 04:25 AM
Hello Paul,
I agree with Amit the neighbor x.x.x.x local-as can be the right tool for this transition.
You may need to play with command options to achieve the desired effect
see
http://www.cisco.com/en/US/docs/ios/iproute_bgp/command/reference/irg_bgp3.html#wp1065665
in a second time you can configure each router with new AS and you can remove the local-as option.
Hope to help
Giuseppe
04-30-2010 06:20 AM
Exactly I agree with above technique...
In fact if you want minimum downtime, then it is the only possible solution i guess.
Regards,
Smitesh Kharecha
04-30-2010 03:17 PM
Thanks everyone. I was already looking into this but wanted to check here to make sure that I was going down the correct path. We're going to do this next Monday and I will post back with status and ratings.
Thanks again,
Paul
05-01-2010 12:30 AM
Hello Paul,
during migration you may need to use route-maps to decide what to advertise to a peer in addition to the use of local-as neighbor command.
this has to be done to avoid to advertise IP address block 1 (associated to ASN1) with a originating AS ASN2 or viceversa
sorry if this is basic stuff, just to be more clear.
Hope to help
Giuseppe
05-01-2010 09:01 AM
Thanks, Giuseppe. This is not basic stuff to me, so I do appreciate it. I am more of a firewall guy who just inherited a very complex BGP
project.
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