Unexpected issues with "nslookup" command

James Roberts-Thomson James.RobertsThomson036 at msd.govt.nz
Fri Apr 16 02:40:06 UTC 2010


Hello,

I have tried to research my problem, but haven't found an answer from the collected Google wisdom of the ages, unfortunately.

We have a situation where we are getting strange results from the "nslookup" command (with knock-on effects to name resolution in general).

We have two primary (internal) name servers; if we select one of our clients, and use either name server by itself in the /etc/resolv.conf file, all works well.  However, specifying BOTH name servers in the /etc/resolv.conf file causes nslookup binary to state ";; Got recursion not available from <first-server-IP>, trying next server", but then successfully returns the name query.

If we reverse the order in /etc/resolv.conf, then the message changes to reflect the changed order.  So, if we have the following /etc/resolv.conf:
domain blah.com
nameserver 1.2.3.4
nameserver 5.6.7.8

running "nslookup client.blah.com" we get:
;; Got recursion not available from 1.2.3.4 trying next server
Server:         5.6.7.8
Address:        5.6.7.8#53

Name:   client.blah.com
Address: 192.168.222.111

and to show what I mean, if we reverse the order so that /etc/resolv.conf contains:
domain blah.com
nameserver 5.6.7.8
nameserver 1.2.3.4

the nslookup output says:
;; Got recursion not available from 5.6.7.8 trying next server
Server:         1.2.3.4
Address:        1.2.3.4#53

Name:   client.query.com
Address: 192.168.222.111

Each name server works fine; each name server works fine when it is the only nameserver listed in /etc/resolv.conf.  The queries on the wire are the same (I've snooped the traffic with TCPDUMP).  The problem continues if I add a third server to /etc/resolv.conf, thus:

example /etc/resolv.conf
domain blah.com
nameserver 127.0.0.1
nameserver 1.2.3.4
nameserver 5.6.7.8

and the output from nslookup:
;; Got recursion not available from 10.163.134.22, trying next server
;; Got recursion not available from 10.35.6.21, trying next server
;; connection timed out; no servers could be reached

(This is how we first noticed the issue - the localhost caching nameserver died, and all name resolution ground to a halt).

This happens on any of the clients running ISC Bind nslookup (I've even recompiled the latest v9.7.0 binary, too).

Can anyone explain what may be happening here, please?

Thanks!

James Roberts-Thomson

(My apologies for the following disclaimer, over which I have no control)


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