We've started having DNS/DHCP issues on our Windows network and discovered that in addition to our server, the LinkSys E2000 router seems to be handing out IP addresses. I assume this is the problem, but I'm not sure. I logged in to the router and noticed that it's set up for "Automatic Configuration – DHCP". The help files say:
"By default,the Router’s Internet Connection Type is set to Automatic Configuration – DHCP, which should be kept only if your ISP supports DHCP or you are connecting through a dynamic IP address."
That being said, should I change the configuration, and if so, to what?
(Sorry, I wasn't here when this was configured so I don't have the background on this.)
The Router should have two different setttings. One to set if to accept a Dynamic Public IP address from Comcast on the Wan Side and the other to act as a DHCP server handing out Private range IP addresses to devices on your local area network.
Usually there is a Status Tab that allows you to see the Public IP address your router is pulling from the Comcast DHCP server. You need to leave the DHCP Client intact on the WAN side.
On the LAN side most people Leave the DHCP server in place on the LAN side but you can turn the Server off if you want to set up Static addresses for the devices on your LAN.
It would help if you detail exactly what your DNS/DHCP issues are, as well as your exact equipment and setup.
Just to echo James' post, you want to leave the setting you point out strictly allow. That is the router's WAN (Wide Area Connection)-side connection setting for Comcast and it's set correctly. Your router requests a public IP address from Comcast via DHCP and it does so based on this setting. If you change it, you will most likely lose your Comcast Internet connection.
As for your issue, I don't really understand what you mean by "in addition to our server". As James points out, your router has two sides, one for the WAN connection (as mentioned above), and one for the private LAN which comprises your home network. The LAN side has a DHCP server (distinct from the DHCP client used on the WAN side) that gives out private IP addresses to the systems on your home network, like computers, laptops, cell phones with WiFi, iPads, printers, TiVo, TV, Xbox/PS3, etc. The vast majority of users leave this function as is and let it assign the IP address for everything on their network. The default configuration for most computers or other network clients is to obtain an IP address via DHCP and if that router function is turned off or restricted too much, they would fail to get proper connections for some or all of their network devices. Some users with more advanced networks or needs will sometimes manually assign an IP address to a server or other device (like a wireless IP camera, etc) and they will make sure the IP address they use is NOT controlled by the router's DHCP server or they might end up with two devices on the same network with the same IP and that would cause big trouble.