UMN:CLI User ManualV8102412A DHCP server may use the remote ID to select the IP address to be assigned. It maypermit static assignment of IP addresses to particular remote IDs, and disallow an ad-dress request from an unauthorized remote ID.IP SpoofingA DHCP client may associate the IP address assigned by a DHCP server in a forwardedDHCP_ACK message with the circuit to which it was forwarded. The circuit access devicemay prevent forwarding of IP packets with source IP addresses, other than, those it hasassociated with the receiving circuit. This prevents simple IP spoofing attacks on the cen-tral LAN, and IP spoofing of other hosts.MAC Address SpoofingBy associating a MAC address with a remote ID, a DHCP server can prevent offering anIP address to an attacker spoofing the same MAC address on a different remote ID.Client Identifier SpoofingBy using the agent-supplied remote ID option, the untrusted and as-yet unstandardizedclient identifier field need not be used by the DHCP server.Fig. 9.38 shows how the DHCP relay agent with the DHCP option 82 operates.Fig. 9.38 DHCP Option 82 Operation9.6.6.1 Enabling DHCP Option 82To enable/disable the DHCP option 82, use the following command.Command Mode Descriptionip dhcp option82 Global Enables the system to add the DHCP option 82 field.no ip dhcp option82 Disables the system to add the DHCP option 82 field.
