DHCP - CSC130

DHCP - What it is

DHCP the Dynamic Host Configuration Protocol and Bootp it's Unix-based cousin are methods whereby a host can have a server configure it's TCP/IP Configuration automatically. On Windows hosts it is very easy to configure DHCP clients in the TCP/IP Control Panel, in fact all you have to do is select Obtain and IP Address Automatically and the host will broadcast on Port 67the BootP port, seeking out a DHCP or BootP server.

Contacting the DHCP Server and getting a Lease

A host that is set to contact a DHCP server will broadcast to find a server that is providing IP address LEASES. See the following Ethereal Screenshot showing the DHCP Discovery and negotiation process. Note the Broadcast address, the address of the host that is trying to obtain a lease 0.0.0.0 (Remember it has no IP yet) and the ACK and ARP request when trying to come on the network.

Release Renew and Leases

The Network Admin is in charge of the server and can make choises like how long a lease runs and what IP address range is offered, along with many other DHCP configuration choices. The client can run winipcfg or ipconfig /all to see their IP configuration and can choose to release and renew their connection to the DHCP server. The release | renew commands can also be entered manually and would take on this syntax m

On a Windows 2000/XP System, the commands would be as follows:

ipconfig /? Shows available ipconfig commands.
ipconfig /release
ipconfig /renew

After the command, you can specify which connection to release (ex. ipconfig /release "Local Connection 1"). If you do not specify a connection, it will release or renew your default connection.

Server Configuration

The configuration of the DHCP server is beyond the scope of this class, but here is a screen shot of our DHCP servers Control Panel

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