Re: IPv6 Deployment for the LAN

[Karl Auer]

On Thu, 2009-10-22 at 11:03 -0400, Kevin Loch wrote:
> > If, on the other hand, the REAL desire is to have a DHCP server break 
> > the tie in the selection between several routers that advertise their 
> > presence, that wouldn't be unreasonable.
> 
> In some configurations not all hosts are supposed to use the same
> router.  We need the _option_ to specify a default gateway and
> have the override any RA's a host may see.

It would be a tool, and if someone wants to use a tool, they can. It
won't be my thumb they hit :-)

But I can't see how a DHCP server can know enough about the routers to
be able to send out useful discrimination information. So it will have
to be manually entered, or come from an IPAM, or...

Nor can I see how the DHCP server can identify the routers to the host
except by their addresses, and these can change or be removed without
the DHCP server finding out.

The only way I can see it working is if the host were smart enough to
compare the DHCP router discrimination info with the information it has
received via RA and delete mismatches, or possibly just revert to using
RA information if any mismatches at all are detected. That would be an
item the DHCP server could specify as well - what to do in case of a
mismatch. It could even be specified on a per-router basis, though the
whole thing seems to be getting a bit unwieldy now.

The DHCP servers will not be on the same subnets as all the routers
involved, so they can't sniff the RAs themselves - unless we set up an
RA relay... hmm.

I don't see DHCP-delivered router preferences as being something that
will "break the Internet". In the vast majority of cases they will be
unnecessary. For those that do need it though, and if it can be done,
why not?

Regards, K.


-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer (kauer@biplane.com.au)                   +61-2-64957160 (h)
http://www.biplane.com.au/~kauer/                  +61-428-957160 (mob)

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