queer dns access problem

[Bill Tangren]

I have two servers that are set up in the same way, except that the one
that is working properly is running RHEL ES 4.6 while the other is running
4.5. I can't update the latter, because DNS is not working properly.
Ordinarily I would poke around until I found the problem, and not bother
y'all, but I'm stumped as to what the problem could be. Except for MAC
address and IP number, the /etc/hosts, /etc/sysconfig/network,
/etc/resolv.conf, and /etc/sysconfig/network-scripts/ifcfg-eth0 files are
identical. Neither run a DNS service. Both are on the same subnet. Both
boxes are running iptables, but turning off iptables doesn't help. I can
ssh into, and ping the broken box. I can ssh out of that box too, if I use
ip numbers. When I try to do an nslookup on the broken box, all I get is:

;; connection timed out; no servers could be reached.

Could someone give me a few clues as to where to look to diagnose this
problem?

-- 
Bill Tangren
U.S. Naval Observatory

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