ipv6 next-hop link-local

Mark Smith nanog at 85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org
Tue Feb 15 22:01:42 CET 2011


On Tue, 15 Feb 2011 21:35:33 +0100
Roger Wiklund <roger.wiklund at gmail.com> wrote:

> My understanding is that all routing protocols that support IPv6 are
> using link-local as next-hop.

I think the idea behind that is that link locals are always present and
independent of any other addressing and it's/their preferred or valid
lifetimes. This isn't a new idea, IPX, Appletalk and IPv4 have
had "this network" prefixes before. In IPv4, it is the node/host
address with all zeros in the network/subnet portion.

> But when I configure a static route I usually use the global unicast
> as next-hop.  When I issue a show route, there is an inconsistency
> where dynamically learned routes have link-local as next-hop and my
> static route has the global unicast.
> Are you making any efforts to keeping it consistent? I.E specifying
> interface and link-local as next-hop even for static routes?

It would make sense to try to keep your routing protocols' next-hops
decoupled from your global or other addresses. To make supporting
static routes easier, you could configure static link local addresses
e.g. fe80::1/64 etc. It probably wouldn't hurt if the SLAAC derived
link-local addresses were left there, although you may wish to disable
them so that all protocols that want to use link locals will use your
statically configured ones.


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