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Re: IPv6 routing /48s

  • From: Jack Bates
  • Date: Wed Nov 19 18:03:54 2008

Christopher Morrow wrote:
6to4 v6 addrs are just regular v6 addrs as far as the network is
concerned. if you put a 6to4 addr on your server you are saying that
you don't have native v6 transport to that host(s) and that you are
reachable via the 6to4 tunnel your host presumably has configured.

Sure it's just another address, except the anycast portion of it for dealing with tunnels. It's also usually set to a different label and priority in windows prefix policies (and at least some linux setups). I was referring to the matter of if a windows box will even choose to use 6to4.

6to4 is just an ip, 128bits long, but an ip... no differentiation is
made in the network for 6to4 vs 'normal v6'... unless someone's
putting up acls, or blackholing 6to4's /16, of course.

Windows and several other end systems use prefix policies to determine if they use IPv6 or IPv4 and even when using IPv6, if they should use the 6to4 tunnel or not.

can you explain this a little more? is it possible your v6 packets hit
something like 6pe inside HE and exit to NTT without hitting a

If a router does not a) know how to encapsulate 6to4 and send it over ipv4 to the destination or b) know how to reach a 6to4 anycast address where the packet can be encapsulated into IPv4, the packet is going to get dropped. Of course, you could be right. could be purposefully not sending icmp replies back to 6to4 addresses for other reasons while replying to my non-6to4 addresses. I hesitate to say filter, as it does push the 6to4 sourced packets on to other networks.