DHCP is used to automatically assign IP-addresses and other network configuration options to networked computers and devices on a local area network.
On a Windows computer, the default option for the IP-address in the TCP/IP protocol settings (under network properties) on is "Obtain an IP address automatically". This will allow a DHCP server (like Simple DNS Plus) to automatically assign the client computer an IP-address, subnet mask, domain name, default gateway and DNS server (Simple DNS Plus automatically assigns itself as the DNS server).
An IP-address is "leased" to a client computer for a configurable length of time known as the "lease period".
This is the maximum time the client computer may use the IP address without getting the lease renewed.
After half the time of the lease period has elapsed, the client computer will begin continuously trying to renew the lease.
IP addresses can be reserved for specific computers based on computer name or hardware address (network card MAC address).
To determine a computers hardware address, on Windows 95/98/Me, run "WINIPCFG" (from Start menu -> Run), select the correct adapter (network card), and see "Adapter Address".
On Windows NT4/2000/XP/2003, run "IPCONFIG /ALL" from a command prompt, and see "Physical Address".
When a DHCP client leases an IP-address, Simple DNS Plus can automatically generate, an A-record and a PTR-record (and zones to keep them in if needed), so that other computers can find it using DNS, just as if the client had a fixed IP-address and the DNS server had records defined for it.
To enable this functionality, use the "Automatically update DNS" setting in the Options dialog / DHCP section.
In DNS, the full domain name of the client will be the computer name (defined under "Identification" in network settings) cleaned of spaces and special characters plus the domain name defined in the DHCP scope.
Simple DNS Plus has a unique option for using DHCP with older Apple/Mac clients and other devices which do not supply a computer name in their DHCP requests.
When first assigned an IP address, the client name will be listed as the client's hardware address as a hexadecimal number, but you can right click on the lease (DHCP Leases View) and "rename" it - giving it a real name, which is both easier to remember and use via DNS. The new device name will be remembered as long as you run Simple DNS Plus, even if the IP address changes.
To configure DHCP, from the main window select Tools menu -> Options -> DHCP section.
To view active DHCP leases, from the main window select View menu -> DHCP Leases.
Additional advanced options for DHCP can be specified in the "sdnsplus.ini" file.
