DNS weirdness

[Rene Bartosh]

I have a whole bunch of computers behind my router. Recently, some of
them have decided that DNS is too much work and have stopped resolving
hostnames...


All of them can ping e.g. 210.55.12.1 (orcons ns) but only some of
them can resolve hostnames, e.g.

***@athlonxp:~$ nslookup 203.109.252.42 203.109.252.42
Server: 203.109.252.42
Address: 203.109.252.42#53

Non-authoritative answer:
42.252.109.203.in-addr.arpa name = tig-nz-akl-ns-42.ihug.net.

***@copper:~$ nslookup 203.109.252.42 203.109.252.42 ;; connection
timed out; no servers could be reached

There are no firewall rules, e.g.
***@copper:~$ sudo iptables -L
Password:
Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination
***@copper:~$

Anything obvious I have missed?

Rene


--
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Work: http://eksion.net/

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[Michael Dittmer]

Rene

Can you get your PC's to do their DNS queries to the router (if it has a
DNS server) and then get your router to forward external queries to the
Orcon DNS servers?

Michael

-----Original Message-----
From: nzlug-***@linux.net.nz [mailto:nzlug-***@linux.net.nz] On
Behalf Of Rene Bartosh
Sent: Friday, 31 March 2006 4:13 p.m.
To: NZLUG
Subject: [nzlug] DNS weirdness

I have a whole bunch of computers behind my router. Recently, some of
them have decided that DNS is too much work and have stopped resolving
hostnames...


All of them can ping e.g. 210.55.12.1 (orcons ns) but only some of them
can resolve hostnames, e.g.

***@athlonxp:~$ nslookup 203.109.252.42 203.109.252.42
Server: 203.109.252.42
Address: 203.109.252.42#53

Non-authoritative answer:
42.252.109.203.in-addr.arpa name = tig-nz-akl-ns-42.ihug.net.

***@copper:~$ nslookup 203.109.252.42 203.109.252.42 ;; connection
timed out; no servers could be reached

There are no firewall rules, e.g.
***@copper:~$ sudo iptables -L
Password:
Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination
***@copper:~$

Anything obvious I have missed?

Rene


--
Personal: http://kirjava.net.nz/
Work: http://eksion.net/

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[Rene Bartosh]

Post by Michael Dittmer
Rene
Can you get your PC's to do their DNS queries to the router (if it has a
DNS server) and then get your router to forward external queries to the
Orcon DNS servers?
Michael

Yes, that works (using the modem as a DNS server) but the the router
hooked to the modem has my local BIND server set as the DNS server to
proxy to anyway,,,

Rene

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[Cliff Pratt]

Post by Rene Bartosh

Post by Michael Dittmer
Rene
Can you get your PC's to do their DNS queries to the router (if it has a
DNS server) and then get your router to forward external queries to the
Orcon DNS servers?
Michael

Yes, that works (using the modem as a DNS server) but the the router
hooked to the modem has my local BIND server set as the DNS server to
proxy to anyway,,,

What is the DNS setup on the clients?

Cheers,

Cliff

[Jim Cheetham]

Post by Rene Bartosh
I have a whole bunch of computers behind my router. Recently, some of
them have decided that DNS is too much work and have stopped resolving
hostnames...

No particular idea at this stage what could be causing it; but I suggest
that you break out slightly better diagnostic tools. Use dig instead of
nslookup, and ethereal to watch your network while queries are being
attempted.

In general, look for changes in the network; remember that DNS is
usually done over UDP and rarely over TCP, and that many nameservers
that used to be "helpful" and reply to anyone's requests are now locking
themselves down, and only answering their primary customers, just as
open SMTP relays used to be common and are now rare. This means that you
should only resolve to the nameservers provided (via DHCP?) from your
ISP, even if other ones historically worked.

-jim

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[Daniel Faulknor]

Post by Jim Cheetham

Post by Rene Bartosh
I have a whole bunch of computers behind my router. Recently, some of
them have decided that DNS is too much work and have stopped resolving
hostnames...

<snip>

Post by Jim Cheetham
In general, look for changes in the network; remember that DNS is
usually done over UDP and rarely over TCP, and that many nameservers
that used to be "helpful" and reply to anyone's requests are now locking
themselves down, and only answering their primary customers, just as
open SMTP relays used to be common and are now rare. This means that you
should only resolve to the nameservers provided (via DHCP?) from your
ISP, even if other ones historically worked.
-jim

Orcon Nameservers (Which i think rene uses) work for me -- i use WxC not
Orcon

--Daniel


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[Rene Bartosh]

Post by Rene Bartosh
I have a whole bunch of computers behind my router. Recently, some of
them have decided that DNS is too much work and have stopped resolving
hostnames...

OK, so I replaced the Zyxel modem I was using with my good old DSE
XH1169 and DNS has started working again. Asterisk couldnt keep a sip
peer up with the zyxel also, so this seems to be good enough evidence
for me to recommend staying away from anything xyxel...

Rene

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