[Dnsmasq-discuss] setting up dynamic DNS?

Jan 'RedBully' Seiffert redbully at cc.fh-luh.de
Mon Sep 10 21:54:18 BST 2007

Adam Hardy wrote:
> Thanks again for the help. Config files appended at bottom for reference.
> Jan 'RedBully' Seiffert on 10/09/07 16:45, wrote:
>> Adam Hardy wrote:
> adam at gondor:~$ cat /etc/resolv.conf
> search localdomain.net
> nameserver

Ok, looks good.

>> Is their default gateway set to isengard? (route -n should say so)
> Yes

Ok, so this works.

>> What's printed to isengards system logs when a client gets an IP?
> isengard dnsmasq[26803]: reading /etc/resolv.conf
> isengard dnsmasq[26803]: using nameserver
> isengard dnsmasq[26803]: ignoring nameserver - local interface
> isengard dnsmasq[26803]: Ignoring DHCP host name arnor.localdomain
> because it has an illegal domain part


here is the problem

> /var/lib/misc/dnsmasq.leases has no hostnames in it.
> Hmmm. Doesn't look good does it? :(

No no, all working within it's spec IMHO ;)

> What do you think could be wrong
> with it? There seems to be something wrong with the hostname I'm sending
> it ('illegal domain name part')

dnsmasq is basicaly fine with the hostname, it does not like the domain
you're client is sending.
It tries to protect you from forgery.
If a client would record itself as www.google.com, and dnsmasq would
believe this, it would forward all your LAN machines for www.google.com
to this machine.

Somehow the "domain=localdomain.net" doesn't do the trick.

But when looking again, arnor (and maybe the other machines) is sending
"$HOSTNAME.localdomain" as hostname?

the final ".net" seems to get eaten...

May you can remove all the references to your domain from your
dhclient.conf, for a test.

> adam at gondor:~$ cat /etc/dhcp3/dhclient.conf |grep -v ^#
> send host-name "gondor.localdomain.net";

This should be the hostname only, or?

> send dhcp-lease-time 3600;
> supersede domain-name "localdomain.net";

drop this, dnsmasq should give out the right domain

> request subnet-mask, broadcast-address, time-offset, routers,
>         domain-name, domain-name-servers, host-name,
>         netbios-name-servers, netbios-scope, interface-mtu;

> send fqdn.fqdn "gondor.localdomain.net";
> send fqdn.encoded on;
> send fqdn.server-update off;

drop all this fqdn stuff for a test

Which version of dnsmasq is this?

> and it also seems to be forwarding the
> query for arnor.localdomain.net up to the internet nameserver.

Thats because dnsmasq could not find an entry in it's own db, and thinks
maybe the upstream server know something about it.

To tell dnsmasq that localdomain.net is local, and it should not ask
upstream about it, you may want to add:
to your dnsmasq.conf

> Adam


> PS here are the files for reference if they help:
> isengard:~# cat /etc/dnsmasq.conf |grep -v ^# |grep -e ^[[:alnum:]]
> domain-needed
> bogus-priv
> filterwin2k
> domain=localdomain.net
> dhcp-range=,,12h
> dhcp-option=1,

> dhcp-option=3,
> dhcp-option=6,
normally you should be able to put in here, so dnsmasq will
automatically fill in the right value for your interface

> log-queries

Fun things to slip into your budged:
Traffic shaping on the loopback interface

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