[c-nsp] IPv6 domain reply Cisco 6509 IPv4 address

Gert Doering gert at greenie.muc.de
Thu Aug 16 10:42:09 EDT 2012


On Thu, Aug 16, 2012 at 10:09:15AM -0400, Chuck Church wrote:
> Weird.  I'm just starting to play around with Juniper stuff now, and noticed
> pretty much the same behavior.  Configured a v4 DNS server, but a lookup
> resulted in a V6 address trying to be used.  Don't have V6 enabled anywhere,
> routing table was empty.  Figured it was some knob I'm not familiar with in
> JunOS.  Didn't get to wiresharking it, but similar.  Would a device be silly
> enough to request an AAAA record out a v4 only interface?  Would a DNS
> server ever hand out an AAAA for a v4 request (perhaps NAT64/DNS64
> intercepting somewhere?)  

DNS transport and DNS content are completely unrelated.

So there's no reason to constrain your queries to the transport that you
happen to be using.

(OTOH, the internal resolver library in use here seems to have missed 
some discussions that happened over the last 10 years, most notably 
"if there is no public IPv6 address on the system, don't ask for IPv6 
adresses by default, or if you do, at least prefer IPv4 before IPv6" - 
getaddrinfo() with AI_ADDRCONFIG).

USENET is *not* the non-clickable part of WWW!
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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