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I have a DNS server on my LAN that the machines in our office need to use.

Some of these machines are laptops which get taken out of the office regularly, so it causes problems if we hard-code the address of the DNS server on these machines.

I was advised to set up a DHCP server to get around this problem, but I'm not sure where to begin with such a task.

If my router already has a DHCP server, I imagine that would be easiest, but I don't know how to check for such a thing or what I would do if I were to find it. Otherwise I just need to set a DHCP server up on my Linux server.

So I guess my question is: is it likely that my router has a DHCP server, and how do I check?

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What brand\model router do you have? –  joeqwerty Sep 30 '10 at 13:06
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3 Answers

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If your router has a web interface, then you should be able to see a tab or link somewhere that says "DHCP". That's where you configure the settings for it. One of the settings will be the DNS server(s) to instruct the clients to use. Please make sure that these DNS servers are configured (and working) to resolve internal names AND public Internet names, otherwise you'll have complaints from your users.

If your router doesn't have a web interface or it does have one, but there is no "DHCP" link anywhere in sight, then most likely it doesn't have DHCP. In that case you will need to set one up yourself.

You can easily check whether there is a DHCP server running on your LAN. Just configure a Windows box to acquire its settings from DHCP and reboot the box. If it gets an address (other than in the 169.254 range, which are self-assigned addresses) then you do have a DHCP server. If it gets a 169.254 address, well, then you don't.

Most linux distros (that I know of) use the ISC DHCP server. Just install the package, read the manual, make a few decisions on your network setup and modify the config files, then reload and off you go. Any additional questions, just ask.

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If you can run your own DHCP server and avoid using your router's DHCP server that is generally better.

Whilst many routers allow you to change DNS settings, in many models all that does is that the address that the router itself forwards your DNS queries to. In those models it does not change the DNS settings given out via DHCP, and your queries still hit the router's DNS proxy, which in many cases have serious bugs.

See http://www.icann.org/committees/security/sac035.pdf

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It depends what type of router it is. If it's a home-grade router it will likely have a DHCP server built in. If it's a proper business grade router it probably won't.

If you look up the router's model/manual it would probably let you know.

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