[c-nsp] Moving a BGP session to different interface

[Jon Lewis]

On Sun, 28 Sep 2014, Nick Hilliard wrote:

> On 25/09/2014 18:19, Randy wrote:
>> I'm tasked with moving a BGP session on a 6500 from a 1GE to a 10GE
>> interface (live environment).   BGP session details are staying the same.
>> The BGP peer IPs (both v4 and v6) are assigned directly to the existing 1GE
>> interface (no SVI, ect).
>>
>> Is it as simple/possible as configure the new interface with the same IP's
>> but in a shutdown state, move the x-connect, shut the old interface and
>> unshut the new interface?   Or will IOS block me from doing this (two
>> interfaces with the same IP) -- in other words, the IPs will need to be
>> removed from the old interface first?
>
> yes, they will need to removed.
>
>> Thanks for any advise or tips on keeping downtime / CLI work to a minimum :)
>
> if BGP uses the address defined on an interface that you need to migrate,
> you will have downtime on that bgp session.  Standard best practice is to
> block all inbound and outbound prefixes on the session, then gracefully
> shut down the session, then migrate the interfaces, then bring bgp back up
> again.  If this is an ebgp session, you will briefly lose connectivity due
> to your upstreams' non-zero MRAIs, so you will need to do this in a
> scheduled maintenance window.

Wouldn't "even better practice" be to use new IPs on the new interface, 
get the interface up, establish BGP (verify at both ends that routes are 
sent/received/accepted), then shut the old session and relinquish the old 
interface IPs?  Done carefully, there should be no downtime.

----------------------------------------------------------------------
  Jon Lewis, MCP :)           |  I route
                              |  therefore you are
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