DHCP Server Settings
DHCP stands for Dynamic Host Configuration Protocol. The DHCP section is where you configure the built-in DHCP Server to assign IP addresses to the computers and other devices on your local area network (LAN).
Enable DHCP Server
Once your D-Link router is properly configured and this option is enabled, the DHCP Server will manage the IP addresses and other network configuration information for computers and other devices connected to your Local Area Network. There is no need for you to do this yourself.
The computers (and other devices) connected to your LAN also need to have their TCP/IP configuration set to "DHCP" or "Obtain an IP address automatically".
When you set Enable DHCP Server, the following options are displayed.
DHCP IP Address Range
These two IP values (from and to) define a range of IP addresses that the DHCP Server uses when assigning addresses to computers and devices on your Local Area Network. Any addresses that are outside of this range are not managed by the DHCP Server; these could, therefore, be used for manually configured devices or devices that cannot use DHCP to obtain network address details automatically.
It is possible for a computer or device that is manually configured to have an address that does reside within this range. In this case the address should be reserved (see DHCP Reservation below), so that the DHCP Server knows that this specific address can only be used by a specific computer or device.
Your D-Link router, by default, has a static IP address of 192.168.0.1. This means that addresses 192.168.0.2 to 192.168.0.254 can be made available for allocation by the DHCP Server.
Your D-Link router uses 192.168.0.1 for the IP address. You've assigned a computer that you want to designate as a Web server with a static IP address of 192.168.0.3. You've assigned another computer that you want to designate as an FTP server with a static IP address of 192.168.0.4. Therefore the starting IP address for your DHCP IP address range needs to be 192.168.0.5 or greater.
Suppose you configure the DHCP Server to manage addresses From 192.168.0.100 To 192.168.0.199. This means that 192.168.0.3 to 192.168.0.99 and 192.168.0.200 to 192.168.0.254 are NOT managed by the DHCP Server. Computers or devices that use addresses from these ranges are to be manually configured. Suppose you have a web server computer that has a manually configured address of 192.168.0.100. Because this falls within the "managed range" be sure to create a reservation for this address and match it to the relevant computer (see Static DHCP Client below).
DHCP WAN Mode
A method of connection where the ISP assigns your IP address when your router requests one from the ISP's server. Some ISP's require you to make some settings on your side before your router can connect to the Internet.
Note: If you are connecting the router to a DSL modem or cable modem, and the modem uses DHCP to assign IP addresses in one of the private subnet ranges (for example, 192.168.0.0 – 192.168.255.255), it is likely that the modem is performing NAT and that connecting the router in DHCP WAN Mode will cause double NAT. Double NAT -- having two NAT devices in tandem -- can cause problems with some networking functions, such as DMZ, port forwarding, and VPN. In this case, it is preferable to use the modem's user interface to disable NAT on the modem, then connect the router using the WAN mode appropriate to the no-NAT state of the modem. For example, some DSL modems allow you to specify that PPPoE is implemented on the router. If you select that option on the modem, you would then select and configure the PPPoE WAN mode of the router.