DNS header format for Query requests

Marc.Thach at radianz.com Marc.Thach at radianz.com
Tue Oct 9 15:47:03 UTC 2001

Sounds like the pesky CD bit (DNSSEC aware resolver) that Kevin so kindly
pointed out to me some time ago.
Marc TXK

                    James Raftery                                                                                  
                    <james-bind-use        To:     bind-users at isc.org                                              
                    rs at now.ie>             cc:                                                                     
                    Sent by:               Subject:     DNS header format for Query requests                       
                    ce at isc.org                                                                                     


I'm trying to diagnose a problem with a piece of equipment that
seems to be sending badly formed DNS queries. I need to get an accurate
description of the Header format for a Query request but the maze
of RFCs is melting my brain.

Is the Header format in RFC1035 still correct and complete for
Opcode 0 (Query) requests? I know it's been amended for other Opcodes,
Update for instance.

Specifically tcpdump is seeing Headers with the fourth byte set to
0x40: which mean the first ``Z'' bit is set. Have any of the Z bits
been defined for Query requests?

James Raftery (JBR54)
  "It's somewhere in the Red Hat district"  --  A network engineer's
   freudian slip when talking about Amsterdam's nightlife at RIPE 38.

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