Re: Why specify a default router?
On Tue, Jul 05, 2005 at 10:24:06AM -0700, The Orange Rider wrote:
> Paul TBBle Hampson wrote:
> > > There're also "non-broadcast multiple access" link layers where router
> > > solicitation might be tricky; I'm not familiar with the details. I think
> > > 6to4 is one such; the IPv4 Internet can be treated as your link layer, but
> > > you can't send a packet to all IPv4 nodes looking for a router.
> >
> > Actually, IPv4 Anycast is supposed to do something like that, except with
> > routing trickery. You send to 192.88.99.1, and IP is supposed to drive your
> > packets to the nearest node that is advertising that address. It's kinda like
>
> I just skimmed my O'Reilly book on IPv6 Essentials and (unless I
> skimmed it wrong) it looks like yes you can either manually configure
> a default gateway to use as a 6to4 relay, or you can send it to a IPv4
> router anycast address and it'll be taken care of. Both ways should
> work. I think RFC 3056 specifies 6to4 with a manual setting and RFC
> 3068 defines the anycast address that can be used.
>
> > the ::ff02 (is that right?) routers-on-link IPv6 multicast link you use to
> > solicit routers.
>
> I'm pretty sure it's ff02::2, but that's because I have a book here in
> front of me =)
>
> > I doubt 6to4 does broadcast router solicition, but I expect it does something
> > similar to directed neighbour discovery when given a new link-local destination
> > address (eg another 6to4 address).
>
> I should probably read up more on 6to4, but everything seems clear so far.
>
> I believe that answers my question. Thanks for the help guys!
>
> Orange
The trouble with the ::192.88.99.1 6to4 routers is that there are few
of them. The best configuration I've found, given that there is no
native IPv6 support from your ISP, is using 6to4 addresses on your LAN
and finding a reliable tunnel broker for upstream (out to the
Internet) traffic that is not 6to4.
It looks like this. You route
2002::/16 via the 6to4 interface.
2000::/3 via the brokered tunnel.
There is not 'discovery' for this configuration on the part of the
router. The LAN connected workstations, though, will benefit from NDP
and the discovery of the default gateway.
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