DHCP Server

DHCP provides the following mechanisms for IP address allocation by a DHCP server:

• Automatic—DHCP assigns an IP address, from a range of addresses defined by the ip local pool command in configuration mode and configured as a pool of addresses by the ip dhcp pool command. The address is assigned to a client for a limited period of time set by the lease command (or until the client explicitly relinquishes the address). The exclude command is used to exclude one or more IP addresses from a DHCP local address pool.
• Manual—A client‘s IP address is assigned by the network administrator using the host command in DHCP host configuration command mode, and DHCP is used simply to convey the assigned address to the client. Enter DHCP host configuration command mode using the hardware-address or client-identifier commands in DHCP pool configuration command mode. The hardware-address or client-identifier command specifies the client hardware address and client unique identifier, respectively.

The S- K- and 7100-Series devices maintain a lease database which contains information about each assigned IP address, the MAC address/unique identifier to which it is assigned, the lease expiration, and whether the address assignment is automatic or static.

In addition to assigning IP addresses, the DHCP server can also be configured to assign the following to requesting clients:

• Default router(s), using the default-router command in DHCP pool configuration command mode
• DNS server(s), using the dns-server command, and domain name, using the domain-name command in DHCP pool configuration command mode
• NetBIOS WINS server(s), using the netbios-name-server command, and node type, using the netbios-node-type command in DHCP pool configuration command mode
• Boot file, using the bootfile command mode in DHCP pool configuration command mode
• DHCP options as defined by RFC 2132, using the option command in DHCP pool configuration command mode
• Next server in the DHCP server boot process, using next-server in the DHCP pool configuration command mode