Re: [Idr] new thread regarding capabilities handling

Enke Chen <enkechen@cisco.com> Thu, 27 April 2017 05:33 UTC

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To: Mikael Abrahamsson <swmike@swm.pp.se>
References: <alpine.DEB.2.02.1704270713380.5591@uplift.swm.pp.se>
Cc: idr@ietf.org, Enke Chen <enkechen@cisco.com>
From: Enke Chen <enkechen@cisco.com>
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Date: Wed, 26 Apr 2017 22:33:34 -0700
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Subject: Re: [Idr] new thread regarding capabilities handling
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Hi, Mikael:

Please take a look at the "BGP Dynamic Capability" draft:

   https://www.ietf.org/archive/id/draft-ietf-idr-dynamic-cap-14.txt

Regards,  -- Enke

On 4/26/17 10:18 PM, Mikael Abrahamsson wrote:
> 
> Hi,
> 
> disregard the part in my last email about asking why all bgp sessions in a peer group are 
> flapped when one changes the config of that peer group. Let's discuss that here instead.
> 
> If I add "address-family ipv4 multicast" to my peer-group and it wasn't there before, all
> router OSes I know will just reset all the sessions. This is baffling.
> 
> I see two problems:
> 
> 1. Why can't capabilities be renegotiated without BGP session restaart?
> 
> 2. Why doesn't it require a command to flap the sessions to adapt to the new configuration?
> If I want to run-through my changed policy-map, I have to "clear soft in" (or out). Why isn't
> there a "clear all-sessions-where-capabilities-have-changed" (paraphrasing).
> 
> Current behaviour is very disruptive. You change a line of config that you might think is a
> minor change, and BOOM, all your sessions are reset and you have a many-minutes outage.
>