The most obvious way to install TCP/IP on all of the PCs in a network is to give each and every one its own unique IP address. This technique is practical for a network of a dozen computers, but it will get much more difficult to implement it on a network with hundreds of PCs.

Not only it is time consuming, it has other drawbacks. You will need to keep a record of all nodes and their IP addresses and you will need to label the individual machine with their unique IP address.

Adding new nodes to the network will be a pain, as you will need to remember the last IP address that was assigned out. Removing nodes will render wasted IP addresses that are difficult to remember it exact address for reuse.

Extending the address block beyond it current subnet will render you having to change all the subnet mask info on the entire network.

Extending public addresses from Internic is even more of a hassle since the new address block assigned will be unlikely to be the same one currently on your network.

This is where DHCP (Dynamic Host Configuration Protocol) assigned network blocks has an advantage. A DHCP server allocates IP addresses to nodes as required and unused addresses are savaged back into the pool for reassigning to others as required.

A network of a few hundred computers is not always completely in use at any given time since staff might be on vacation or sick leave. This fact allows you to use few addresses than you have devices, which buys you some time to expand without changing the address if the above scenario occurs.

A DHCP server\'s main purpose is to keep track of a pool of addresses called a scope. A scope defines a range of address from any available DHCP server. When a PC connects to the network, it requests assignment from an address from any DHCP server. This is done via a broadcast and any DHCP server in the network will answer the request and offers a lease of a specific address.

The client will accept one of the lease address available from a list of DHCP servers if there are more than one, and negative acknowledge (reject) the rest of the offers.

The client machine will also obtain various configuration information like gateway address, subnet mask, DNS information, etc from the DHCP server.

DHCP server software is built into most of the server operating systems. Client IP addresses are leased and not static and a lease duration is set.

The server communicates with the client only when the client initiates the contact. Any changes made to your DHCP server, such as creating new address pools or exclusions, will not be known to the client until they attempt to renew their lease.


TCP/IP with DHCP | DHCP Lease Request Details Main Page