Re: OS X Lion and IPv6

[Dario Ciccarone <dciccaro () cisco com>]

> I noticed that my router (a Apple Time Capsule) is advertising it's
> link-local address as default gateway. Changing this manually on my OS X
> host to the global address fixes the problem with scanning global addresses
> as root. As far as I can tell from a few Google searches it seems as if
> Apple Airport and Time Capsule advertise their link-local address as the
> default gateway. To the best of my understanding this should be a valid
> configuration, as it seems to work for other applications ie. browsing the
> web etc ...
That's isn't a completely accurate description of how this works :)

> From the beginning - RFC-4861, section 4.2 - "Router Advertisement
Message Format", IP Fields - "Source Address: MUST be the link-local
address assigned to the interface from which this message is sent.

Router Lifetime <snip>A lifetime of 0 indicates that the router is not a
default router and SHOULD NOT appear on the default router list</snip> -
there is more relevant text.

And then on 6.3.4, Processing Received Router Advertisements - <snip>On
receipt of a valid RA, a host extracts the source address of the packet
and does the following:

- If the address is not already present in the host's Default Router
List, and the advertisement Router Lifetime is non-zero, . . . .</snip>

So your default route(s) should indeed have as a next-hop the link-local
address for the router(s) from which you got that information from.
That's how it should be done - not that "should be a valid
configuration", but that it is THE valid configuration :)


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