update failed: 'RRset exists (value dependent)' prerequisite not

[Barry Finkel]

lartc at manchotnetworks.net" <lartc at manchotnetworks.net> wrote:

>i have 9.2.1-9 running on an up2date red hat 8 box.
>
>whil trying to implement ddns (dhcp updates dns) i noticed that the
>client is able to register its address in the reverse zone, however, the
>forward zone is not updated and the named.log gives the error in the
>subject line of this message.
>
>can anyone comments on why this is happening?

Read RFC 2136 (Dynamic DNS).  The message

     update failed: 'RRset exists (value dependent)' prerequisite not

means that one (or more) of the prerequisite conditions in the DDNS
packet was not satisfied in the zone, so the DDNS update was rejected.
For example, if the DDNS packet contained

     if (zzz.example.com is not a CNAME) and (there is no "A" record for
     zzz.example.com), then add "zzz.example.com.  IN  A  192.168.4.6".

and there were in DNS either of these two entries

     zzz.example.com.  IN   CNAME www.example.com.
or
     zzz.example.com.  IN   A  192.168.8.12

in the zone, then the DDNS update would fail with the above message.
To determine what pre-req is failing, you would have to sniff packets
or get BIND to log all of the incoming traffic.  I have packet traces
from an MS W2k DHCP server, but I have never traced an ISC DHCP server,
so I do not know the contents of any pre-req section.
----------------------------------------------------------------------
Barry S. Finkel
Computing and Instrumentation Solutions Division
Argonne National Laboratory          Phone:    +1 (630) 252-7277
9700 South Cass Avenue               Facsimile:+1 (630) 252-4601
Building 222, Room D209              Internet: BSFinkel at anl.gov
Argonne, IL   60439-4828             IBMMAIL:  I1004994