Re: RFC3484 destination address selection rule 2 is buggy

On Tue, 25 Mar 2008, JINMEI Tatuya / ???? wrote:
> v4:{site-local,global} is special and is not that harmful as long as
> the network is properly configured (I know we cannot always assume
> that, though).  When a link-local address is the only available
> address for host, there should normally be no IPv6 default router
> either.

The scenario where a router advertises the default route yet does not 
advertise any prefix information (or prefix information does not set 
the autoconfig bit) is still a valid scenario (e.g., I could imagine 
DHCPv6-only deployments using this; in fact I believe if you want to 
run DHCPv6-only this is the only choice to for deploying default 
route) and it should be addressed.

Iljitsch noted in the original mail that his default route existed 
even though he moved to ietf-464nat network (the nexthop was answering 
to ping but was not sending RAs).

It is true that the case made in draft-ietf-v6ops-v6onbydefault-03 is 
already somewhat mitigated by implementations which no longer 
implement the "on-link by default" rule but that alone does not seem 
sufficient.

Is moving from one network to another (using the same interface) a 
scenario where you should purge the default route? (Even if the 
nexthop is still responsive?)  Should you purge the default route if 
the link goes down (I suspect not -- e.g. with 802.11 link with bad 
coverage this could be a problem)?

It seems to me that there are also valid scenarios where exactly the 
same problem appears in addition to many scenarios which are usually 
due to misconfiguration.  I believe our protocols should be robust 
enough to cover both valid scenarios and (if there aren't major 
drawbacks) common misconfigurations.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
--------------------------------------------------------------------
IETF IPv6 working group mailing list
ipv6@ietf.org
Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
--------------------------------------------------------------------