From: Petr Lapukhov (petr@internetworkexpert.com)
Date: Fri Jun 16 2006 - 18:32:09 ART
Sami,
for, um, some strange reason, I'm not asleep yet ;))
Hope that won't hurt much ;)
---As to 6to4 tunnels. The idea is pretty simple: 6to4 defines only "encapsulation" method. Everything else - the rules for routing path determination, for instance - remains the same (longest match criteria).
So that encapsulation rule says - if RIB tells us to direct packet to 6to4 tunnel, you take 2nd and 3rd part of destination ipv6 address, and convert it to IPv4 endpoint. Actually, you dont need to use 2002::/16 prefix anytime, this is just for a global "reference" point, so that people may have sensible prefixes around the globe :)
The rest of task is up to routing, which is based on longest match criteria, static routing, etc.
Now, if your router has a bunch of ipv4 addresses, which one you should use for 6to4 tunnel "termination"? Actually, that depends. It sound reasonable to take ipv4 loopback as tunnel "source", since it more convenient. The main thing is that every ipv4 prefix gives you /48 of IPv6 address space, and you may subnet it any way you like :)
So now, it makes sense to use something like:
interface tunnel 0 tunnel mode ipv6ip 6to4 tunnel source loopback0 ipv6 address 1234:101:101:8000::1/56
So you see, there is no 2002::/16 here, nor /64 is the prefix length. But router will take any packet destinied to subnets of 1234:101:101:8000::/56, and encapsulate it via "6to4" method.
I'll try to give more conscious explanations next day :)
HTH
-- Petr Lapukhov, CCIE #16379 petr@internetworkexpert.com
Internetwork Expert, Inc. http://www.InternetworkExpert.com Toll Free: 877-224-8987 Outside US: 775-826-4344 24/7 Support: http://forum.internetworkexpert.com Live Chat: http://www.internetworkexpert.com/chat/
This archive was generated by hypermail 2.1.4 : Sat Jul 01 2006 - 07:57:33 ART