v6 & DSL / Cable modems [was: Private use of non-RFC1918 IP space (IPv6-MW)] (IPv6-MW)

Jack Bates jbates at brightok.net
Thu Feb 5 16:42:08 UTC 2009

Iljitsch van Beijnum wrote:
> So how do you plan on doing that?
It works fine to my house.

> We know that IPv6 runs really well over regular ethernet or over 
> tunnels. It doesn't work so well over the weird crap that broadband ISPs 
> use which superficially looks like ethernet or PPP but isn't (and IPv6 
> over PPP is very problematic).

Not sure on PPP, but I'd suspect there's an issue still of support on 
the CPE side. Cisco's implementation of PPPoE/A and IPv6 seems to be 
easy enough.

Unfortunately, I hate PPP, and the rules between v4 and v6 for RBE have 
changed. Latest Cisco philosophy I read is a /64 per sub-interface, 
stateless dhcp, and PD. The /64 assignments, while a bit messy (as if 
the config wasn't already messy) isn't a big deal. I haven't seen very 
many home routers handling PD, so I can expect that only customers 
without routers will actually use v6. Perhaps a few airports might do 
PD. Don't have one to test.

While not perfect, I don't see much of an issue with the layout, 
although I hope Cisco adds TA to DHCPv6 soon, as there's no telling what 
home routers will decide to do. I have three large issues I haven't 
resolved yet. I have suboptimal paths for v6 compared to v4, and given 
the economy and the expense of upgrading core infrastructures, I do 
wonder if some of these companies will even survive the transition. 
Another issue is my own ignorance, but I still need to play with DNS in 
relation to IPv6, both using DDNS as well as using various support for 
generating templated PTR/A records on the fly. Finally, the by IP theory 
of SII and my CALEA gear definitely won't work well with the current 
IPv6 layout and privacy extension able to change the IP every so often.

I'm still surprised that I haven't seen support for dynamically 
allocating (perhaps through radius) a /64 to a sub-interface based on 
it's receipt of a router solicitation. The dynamic nature of prefixes is 
still preferred if one values some amount of privacy on the Internet. I 
dislike people tracking customers by prefix. How long does it take for 
someone to pinpoint that a prefix won't change and start cataloging more 
information based on prefix that wasn't previously available via cookies?

The only large caveat I've seen with Cisco is that for a 7200 VXR using 
RBE, 12.3T is about as far as you can go with tolerable bugs.

Juniper didn't seem able to provide me with a decent plan comparable to 
Cisco's bridging edge. Perhaps I'm just running obsolete edge gear and 
haven't met the vendors everyone else liked better.


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