Dynamic Host Configuration Protocol (DHCP), an extension of the Bootstrap Protocol (BootP), dynamically provides host configuration information to workstations. To lower administrative overhead, network managers prefer to configure a small number of DHCP servers in a central location. Using few DHCP servers requires the routers connecting to the subnets or bridge (or VLAN) domains to support the BootP/DHCP relay function so that hosts can retrieve the configuration information from servers several router hops away.
User datagram protocol (UDP) is a connectionless protocol that adds reliability and multiplexing to IP. It describes how messages reach application programs within a destination computer. Some network applications, such as the NetBIOS name service, rely on a UDP broadcast to request a service or to locate a service. By default, broadcasts are not forwarded by a router. UDP broadcast forwarding is a generalized mechanism for the router to selectively forward UDP broadcasts.
Important
BootP/DHCP relays are supported only on IP routed port-based VLANs and protocol-based VLANs.
You must enable DHCP relay on the path for port or VLAN configuration to take effect.