topic Re: Problems with DNS-Configuration in Operating System - Linux

Problems with DNS-Configuration

Daniel Schneider — Mon, 04 Feb 2002 08:22:12 GMT

Hi all,
I have a problem with the setup of DNS-Entries on my Linux-router or Clients
The router is on SuSE Linux 7.3, and it is used as Internetgateway for two Win98-Clients.
So I have given the clients the IP's from the Nameserver of my Provider. The result is, that the clients regular to the internet, to get some local Network informations.
I have tried to start the Nameserverdaemon on the linux router, but it is not possible to connect to the internet.
with netstat -nr, I can see, that when the client attempts to connect to the internet, the router connects to the nameserver of the provider, but didn't establish the connection.
I have started the Nameserverdaemon with YAST and the IP from the router is given as DNS in Win98 Networking properties.

What is the right DNS setup for the Win98 client?
What to setup on the router?

The router has IP 192.168.15.1, and the clients 192.168.15.2 ....

Thanks for all help

Best Regards
Daniel :-)

Re: Problems with DNS-Configuration

Vincent Stedema — Mon, 04 Feb 2002 10:51:26 GMT

Hi Daniel,

Here are a few options.

LOCAL LAN:

You can either set up the name server daemon on your router to serve the 192.168.15 zone, or you can create a hosts file for all machines in your LAN and copy it to C:\WINDOWS\SYSTEM32\DRIVERS\ETC on your WIN98 clients.

INTERNET:

A. Configure the name server daemon on your router to forward all DNS requests to your ISP's name servers.
In that case, you need to set your router as the primary DNS server on the clients.

B. Setup firewalling, ip masquerading and/or NAT and allow connections to port 53(?) of your ISP's name servers. The clients will connect through your router to the name servers of your ISP. NAT / ip masquerading will prevent your local ip addresses from being exposed to the internet.
If you choose this type of configuration, you have to set the ISP's name servers as DNS servers on the clients.

This can be a bitch to set up, so you might want to look into using FreeSCO -- http://www.freesco.org . It's specifically designed to be used as a router.

Hope this helps.

Vincent

Re: Problems with DNS-Configuration

Bill Thorsteinson — Wed, 13 Feb 2002 20:01:27 GMT

Your IP addresses aren't valid on the network so, you must to setup NAT (network address translation) also known as masquerading.

If you have a firewall setup you also need to allow connections out to port 53 on both UDP and TCP protocols. This should be from unprivileged ports only.

If you setup DNS you will need the to set-up several files including a file for the root servers. Check out the BIND howto at www.linuxdoc.org, or under /usr/docs on you server.

Re: Problems with DNS-Configuration

Kodjo Agbenu — Mon, 18 Feb 2002 21:06:38 GMT

Hello,

Vincent and Bill gave you what I think is the right solution :
-> Use Masquerading (NAT) because your local IP addresses are not valid on the Internet
-> Set up your Linux box to allow traffic on TCP port 53 (DNS).

I would just add a comment on the second point : I would suggest you to configure your Linux router to act as caching-only name server.
To do so, edit /etc/named.conf as follows :

options {
directory "/var/named";
};

zone "." IN {
type hint;
file "db.cache";
};

zone "localhost." IN {
type master;
file "db.local";
allow-update { none; };
};

zone "127.in-addr.arpa." IN {
type master;
file "db.127";
allow-update { none; };
};

Some distributions of BIND use other names for /var/named/db.cache, db.local or db.127 :

-> named.ca / localhost.zone / named.local
-> root.hint / localhost.zone / 127.0.0.zone
-> etc...

Make your "named" automatically started at boot using chkconfig on RedHat, or manually adding symlinks from /etc/rc.d/rc[2345].d/S99named to /etc/rc.d/init.d/named.

At the end, configure the win98 boxes to use your Linux router as DNS server.

Good luck.

Kodjo