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Understand the DHCP lease process for Windows 2000 Server

DHCP is a very simple and efficient protocol in Windows 2000 Server. When clients request an IP address and other configuration data from DHCP, they don't have full TCP/IP initialized (because they don't have an IP address), so instead they use broadcasts to find DHCP servers. Get the basics on the DHCP lease process.

DHCP is a very simple and efficient protocol in Windows 2000 Server. When clients request an IP address and other configuration data from DHCP, they don't have full TCP/IP initialized because they don't have an IP address, so instead they use broadcasts to find DHCP servers.

The first packet broadcast is DHCPDiscover. As the name indicates, the client tries to discover all DHCP servers on the network. Because the client doesn't have a valid IP address, it uses 0.0.0.0 as the source address and sends the packet as a broadcast to a local network.

When DHCP servers get this packet and they have an IP address to lease to the client, they reply with DHCPOffer. This contains the IP address and additional configuration information (like subnet mask and default gateway) that the DHCP server can lease to the client.

Sometimes clients might receive multiple DHCPOffer packets from several different DHCP servers. In this case, they select the server that responded first and send it the DHCPRequest packet. This packet confirms which DHCP server (and thus which IP configuration data) was selected. All other DHCP servers rescind their offers, and the chosen one sends a DHCPAck message.

DHCPAck acknowledges the lease and provides additional configuration data. Once clients have this packet, they have all the TCP/IP configuration data they need to communicate with other computers that use the TCP/IP protocol.

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