So... is it time to do IPv6 day monthy yet?

Mark Andrews marka at
Mon Jun 20 01:42:34 UTC 2011

Adding AAAA records for existing nameservers will NOT cause TC to
be set where it would not be set without AAAA records unless you
do a "ANY" lookup of the nameserver where it MAY result in TC being

All current implementations, including named, fail to set TC when
adding glue records to a referral in contradiction on RFC 1034.
This issue has been raised with the IETF dnsext wg.  Fixing this
would result in most COM/NET referrals, from the root, setting TC.

Note: recent version of named will add glue which matches the
question section is added to a referral in preference to other glue
and if that glue rrset won't fit it then named will set TC to prevent
the resolution process getting wedged.  Usually only EDNS/512 +
DO=1 queries result in a referral which fits the critera to set TC
even then most such queries don't.

Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at

More information about the NANOG mailing list