Configuring DHCP This section provides information about configuring DHCP. Prerequisites for Configuring DHCP, on page 1 Restrictions for Configuring DHCP, on page 2 Information About DHCP, on page 2 How to Configure DHCP, on page 11 Feature History for DHCP, on page 21 Prerequisites for Configuring DHCP The following prerequisites apply to DHCP Snooping and Option 82: • You must globally enable DHCP snooping on the switch. • Before globally enabling DHCP snooping on the switch, make sure that the devices acting as the DHCP server and the DHCP relay agent are configured and enabled. • If you want the switch to respond to DHCP requests, it must be configured as a DHCP server.
• Before configuring the DHCP snooping information option on your switch, be sure to configure the device that is acting as the DHCP server. You must specify the IP addresses that the DHCP server can assign or exclude, or you must configure DHCP options for these devices. • For DHCP snooping to function properly, all DHCP servers must be connected to the switch through trusted interfaces, as untrusted DHCP messages will be forwarded only to trusted interfaces. In a service-provider network, a trusted interface is connected to a port on a device in the same network. • You must configure the switch to use the Cisco IOS DHCP server binding database to use it for DHCP snooping.
• To use the DHCP snooping option of accepting packets on untrusted inputs, the switch must be an aggregation switch that receives packets with option-82 information from an edge switch. • The following prerequisites apply to DHCP snooping binding database configuration: • You must configure a destination on the DHCP snooping binding database to use the switch for DHCP snooping. • Because both NVRAM and the flash memory have limited storage capacity, we recommend that you store the binding file on a TFTP server. Configuring DHCP 1