[j-nsp] RA Discovery and link-local addressing

Phil Mayers p.mayers at imperial.ac.uk
Wed Jan 27 08:11:32 EST 2010

On 27/01/10 12:06, Ben Dale wrote:
> Hi All,
> I don't seem to be able to find a definitive answer to this one
> either in Juniper's docs, or the very dry RFCs I've been ploughing
> through but:
> I have an SRX (9.6) running a small IPv6 network (a tunnel and a /48
> provided by HE).  I have statically allocated a /64 from the /48 to a
> vlan interface and enabled RA.  Host machines (OSX 10.6.2) on that
> VLAN are discovering addresses from that range correctly, and traffic
> is being forwarded as expected, but the address they learn for their
> router is actually the link-local address on the SRX vlan interface,
> rather than the static address that I would expect.

That's normal. Since communication with a router is via the local link, 
the "next hop" of an RA is the link-local address.

It's perfectly possible (if confusing) for a router to not have an 
address within the prefix, but still advertise it.

This puzzles people in Cisco-land with HSRPv6, where the address which 
is floated is also link-local.

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