An odd IPv6 application issue

Fred Baker fred at
Sat Dec 11 06:37:08 CET 2010

On Dec 10, 2010, at 9:06 PM, George Bonser wrote:

> When it does so, it sources traffic from ::ffff:  rather than
> 2620:0:5103:1234::3

So it is selecting the IPv4-Mapped IPv6 Address derived from the IPv4 address (RFC 4291 section

It sounds like the RFC 3484 tables are screwed up. The default table (from the RFC) is:

      Prefix        Precedence Label
      ::1/128               50     0       # loopback
      ::/0                  40     1       # any IPv6 address
      2002::/16             30     2       # any "normal" IPv6 address
      ::/96                 20     3       # IPv4-Compatible IPv6 Address
      ::ffff:0:0/96         10     4       # IPv4-Mapped IPv6 Address

It is supposed to compare the addresses is has options on and select the one with the longest common prefix. Tell me that the name you're trying to connect to doesn't have in a AAAA record an IPv4-Mapped IPv6 Address?

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