If you don't know what a dhcp server is then you probably don't need to read this. Although I have a dsl modem/router that's capable of serving up dhcp to my home network I don't use it. I setup my own on an Ubuntu server. The reason is so I can configure dhcp to be aware of my dns server and control its functioning. Also, I just don't trust my dsl modem/router to do "everything" inside my network.

1. Installing a DHCP Server on Ubuntu
   The good news is that this is really, really easy. The bad news is you have to understand networking some to grok what this all means.
   1. Install DHCP
      Lets download and install it:
      

      Remove udhcpd

      Somehow I got an alternative dhcp server installed named udhcpd. This messed everything up for a while. Remove it if you have it first:
      

      sudo apt-get remove udhcpd

      sudo apt-get remove udhcpd

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      sudo apt-get install dhcp3-server

      sudo apt-get install dhcp3-server

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   2. Configure DHCP
      Now lets configure the main dhcp config file.
      

      sudo nano /etc/dhcp3/dhcpd.conf

      sudo nano /etc/dhcp3/dhcpd.conf

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      /etc/dhcp3/dhcpd.conf

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       1 subnet 192.168.0.0 netmask 255.255.255.0  2 {  3 range 192.168.0.5 192.168.0.200;  4 option domain-name-servers 192.168.0.2;  5 option domain-name "bxgrant.com";  6 option routers 192.168.0.1;  7 option broadcast-address 192.168.0.255;  8 default-lease-time 600;  9 max-lease-time 7200; 10 }

      subnet 192.168.0.0 netmask 255.255.255.0 { range 192.168.0.5 192.168.0.200; option domain-name-servers 192.168.0.2; option domain-name "bxgrant.com"; option routers 192.168.0.1; option broadcast-address 192.168.0.255; default-lease-time 600; max-lease-time 7200; }

      Line 1.

      This is either going to bet 192.168.0.0 or 10.0.0.0 depending on which range you want to use for your internal IP address range. I use 192.168.0.0 so IPs in my internal network are 192.168.0.x.

      Line 3.

      This is the range of addresses the DHCP server should hand out. I only wanted addresses from 5 - 200 in the range handed out.

      Line 4.

      Change the IP address on this line to be the address of your dns server.

      Line 5.

      Replace bxgrant.com with your own internal domain.

      Line 6.

      Replace the IP address on this line with the address of our dsl modem/comcast router or whatever IP address you get your Internet from. I use dsl so 192.168.0.1 is the address of my dsl router.

      Line 7.

      This is the IP of the last number in the range you're using (just make sure the last number is 255).

      
      Lastly some distributions of ubuntu don't send the host-name of the domain with requests by default. Lets check and make sure it is.
      

      sudo nano /etc/dhcp3/dhclient.conf

      sudo nano /etc/dhcp3/dhclient.conf

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      dhclinet.conf Host Name Check

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      1 send host-name "bxgrant.com";

      send host-name "bxgrant.com";

      Line 1.

      Make sure there's a line in the file that's NOT commented that starts with "send host-name" and then modify the domain to reflect your network. If it's not there add it. If it's commented, uncomment it and add your domain.
   3. Start/stop/restart DHCP
      sysvconfig

      I use "sysvconfig" to manage services so the code below won't work unless you install sysvconfig:
      

      sudo apt-get install sysvconfig

      sudo apt-get install sysvconfig

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      Then to start/stop/restart your dhcp server:
      

      sudo service dhcp3-server start sudo service dhcp3-server stop sudo service dhcp3-server restart

      sudo service dhcp3-server start sudo service dhcp3-server stop sudo service dhcp3-server restart

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