Re: [v6ops] PD to hosts [was: DAD again [was: draft-ietf-v6ops-host-addr-availability discussion] ]

["Templin, Fred L" <[e-mail]>]

Hi Philip,

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On Behalf Of Philip Homburg
> Sent: Monday, November 16, 2015 2:15 PM
> To: [e-mail]
> Cc: Templin, Fred L
> Subject: Re: PD to hosts [was: DAD again [was: draft-ietf-v6ops-host-addr-availability discussion] ]
> 
> >> I wonder if A should then always set the Router flag in neighbor advertis=
> >ements
> >> as well. It looks like it has to, otherwise the neighbor cache will be
> >> flushed.
> >
> >Section 8.3 of RFC4861 says:
> >
> >   "If the Target and Destination Addresses are the same, the host MUST
> >   treat the Target as on-link.  If the Target Address is not the same
> >   as the Destination Address, the host MUST set IsRouter to TRUE for
> >   the target.  If the Target and Destination Addresses are the same,
> >   however, one cannot reliably determine whether the Target Address is
> >   a router.  Consequently, newly created Neighbor Cache entries should
> >   set the IsRouter flag to FALSE, while existing cache entries should
> >   leave the flag unchanged.  If the Target is a router, subsequent
> >   Neighbor Advertisement or Router Advertisement messages will update
> >   IsRouter accordingly."
> >
> >and Appendix D. of RFC4861 says:
> >
> >   " - The target of the redirect, when the target is the same as the
> >      destination, does not carry any host vs. router information.  All
> >      that is known is that the destination (i.e., target) is on-link
> >      but it could be either a host or a router."
> >
> >In this case, the Target and Destination Address are the same. So, there is
> >no host vs. router information, and the default value for isRouter is FALSE=
> 
> Target and Destination are the same if the router sending the redirect
> considers the Destination to be on-link.
> 
> Given that the router has a link local next hop, I wonder if that's the
> case.
>
> In general after prefix delegation, the delegating router is supposed to
> assume that the prefix is not on-link but used on other links.

Yes, you are right; the target address will be the link-local address of
N on the eth0 link, and the destination address will be A. So, to the
outside world, N would look like a router. Do you see a problem
with that?

Thanks - Fred
[e-mail]