An odd IPv6 application issue

George Bonser gbonser at seven.com
Sat Dec 11 07:37:37 CET 2010


And to make matters worse, I can't use telnet to troublshoot because if
I say something like:

telnet -b host-a.mydomain.com foo

I get:

telnet: could not resolve host-a.mydomain.com: Name or service not known

even though it is in /etc/hosts

while:

ping6 host-a.mydomain.com
64 bytes from host-a.mydomain.com: icmp_seq=1 ttl=64 time=0.020 ms

So far this is turning into a huge can of worms.  Everything seems to
resolve things in different ways.





> -----Original Message-----
> From: ipv6-ops-bounces+gbonser=seven.com at lists.cluenet.de
[mailto:ipv6-
> ops-bounces+gbonser=seven.com at lists.cluenet.de] On Behalf Of George
> Bonser
> Sent: Friday, December 10, 2010 10:21 PM
> To: Fred Baker
> Cc: ipv6-ops at lists.cluenet.de
> Subject: RE: An odd IPv6 application issue
> 
> >
> >
> > On Dec 10, 2010, at 9:06 PM, George Bonser wrote:
> >
> > > When it does so, it sources traffic from ::ffff:10.1.2.3  rather
> than
> > > 2620:0:5103:1234::3
> >
> > So it is selecting the IPv4-Mapped IPv6 Address derived from the
IPv4
> > address (RFC 4291 section 2.5.5.2).
> >
> > 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?
> 
> The name I am trying to connect to: A: has neither an A record nor an
> AAAA record.  B: It exists only in /etc/hosts.  C: The name I am
trying
> to connect to is not on the same subnet as the source machine:
> 2620:0:5103:2000::3/64  D: the source machine has a default gateway on
> the same subnet as the desired source IP.
> 
> 



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