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route converge time

On Sat, Nov 28, 2015 at 10:45 PM, J?rgen Jaritsch <jj at anexia.at> wrote:

>> From: Matthew Petach [mpetach at netflight.com]
>> Or, better yet, apply a REJECT-ALL type policy
>> on the neighbor to deny all inbound/outbound
>> prefixes; that way, you can keep the session
>> up as long as possible, but gracefully bleed
>> traffic off ahead of your work.

> Route update via new policy could be more cpu intensive than dropping prefixes caused by session shutdown.

Of course. But operable routes remain throughout.

However, you don't want to reject the routes you want to depreference
them, both received and sent. And depreference them on the router
whose link will stay up first, so that it starts sending traffic via
its link before the router you're taking down changes its routes. Once
the preference change moves all routes to the other router, then you
want to drop the BGP session to deal with the residual routes. Then
once traffic drops to zero on the link, you take down the link.

If your customers are really that sensitive to downtime during a
reasonable off-hours maintenance window.

Bill Herrin

William Herrin ................ herrin at dirtside.com  bill at herrin.us
Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>