Re: [v6ops] draIn ft-ietf-v6ops-design-choices WGLC

[Gert Doering <[e-mail]>]

Hi,

On Fri, Apr 10, 2015 at 06:02:22PM +0100, Nick Hilliard wrote:
> On 10/04/2015 16:42, Ackermann, Michael wrote:
> > It seems that the advice to use Link Locals for next hop (or maybe even
> > to use them at all?),  is situationally dependent.
> 
> Can you provide some concrete examples of where LLs are more appropriate
> than GUAs for BGP NH, and why?  I'm genuinely struggling to see any advantage.

Seconded.

LL NHs for BGP are one of the things causing serious pain today (you peer
with a peer router on the GUA, your BGP process installs the prefix with
the LL NH into the FIB, and if anything breaks in ND for the LL NH, you
blackhole traffic - with GUA NHs, if ND breaks for the GUA, BGP will not 
come up, so "no blackholing").  

And no, this is not a hypothetical example, we currently have at least 
one peer configured with static ND entries on our side because LL ND between
these two boxes is "unreliable", and we've seen blackholing as a consequence
(TAC investigating, but it's... complicated to debug ND on a shared network
with over 600 routers and significant traffic levels).

Gert Doering
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have you enabled IPv6 on something today...?

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