ipv6 next-hop link-local

Mark Smith nanog at 85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org
Sat Feb 19 11:26:00 CET 2011


On Sat, 19 Feb 2011 11:07:22 +0100
Gert Doering <gert at space.net> wrote:

> Hi,
> On Sat, Feb 19, 2011 at 08:31:29PM +1030, Mark Smith wrote:
> > > Our operational problems come from networks that only have eBGP 
> > > speakers - namely, exchange point meshes - and link-local next-hops
> > > have no reason for existance there.  No RIPng, no ICMP redirects.
> > 
> > I think they can have a place there. If your exchange point eBGP
> > routers "next-hop self" when they distribute routes into iBGP, then the
> > eBGP next hops are only visible to the eBGP router. Using link locals
> > (static link locals if you like) for that can provide the benefit of
> > making you eBGP relationships independent of the global addressing that
> > is being used on the exchange point mesh. 
> Of course one could run an exchange point on link-local addresess - but
> I have not ever seen one yet, and I do not think that the operational
> difficulties will outweigh the benefits.
>  (Which benefits, exactly?  
> Exchange points usually renumber their fabric when they run out of
> available addresses for participant routers - which won't happen 
> which IPv6).

There's no real need for GTSM if link locals are used, and the threat of
SYN or similar control plane attacks from off-link sources disappears.

> Is *anyone* running eBGP on link-locals?
> Gert Doering
>         -- NetMaster
> -- 
> did you enable IPv6 on something today...?

I think the fact that you're putting that in your signature indicates
we really shouldn't be making judgements about what will be common IPv6
practice at this stage of IPv6 deployment. I think most people will be
applying IPv4 thinking to IPv6 deployments, so they may not be aware
that link-locals can be used for this purpose. 5 to 10 years time might
be a better time to observe what is common practice.


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