3Com 10014299 manual Configure interface relay address, Ip relay-address ip-address

Configure DHCP Relay 345

Figure 127 Schematic diagram of DHCP relay

DHCP client

Network

DHCP trunk router

DHCP server

DHCP client

The above figure is the schematic diagram of DHCP relay. Its working principle is as follows:

After starting DHCP client, a configuration request message is broadcast and the DHCP relay router will send the message to the designated DHCP server on the other network after processing it properly. According to the information provided by the client, the server sends configuration information to the client via DHCP relay and completes the dynamic configuration of host.

DHCP relay actually realizes transparent transmission of broadcast messages, i.e. transmitting broadcast messages of DHCP clients to DHCP servers on other network segments. Besides, the user can also configure transparent transmission for broadcast messages of designated protocols as required, to enable specific protocol broadcast messages of this network segment to arrive at other network segments. Similarly, the destinations are specified by IP auxiliary addresses. For example, transmit TFTP and DNS protocol messages transparently to corresponding servers.

To implement the DHCP relay, users have to configure IP auxiliary addresses to specify the DHCP server addresses.

Configure DHCP Relay DHCP configuration includes:

■Configure interface relay address

■Configure transparent transmission forwarding protocol.

1Configure interface relay address

To implement DHCP relay function, you need to configure IP relay address to specify DHCP server address. For DHCP relay, IP relay address specifies DHCP server. After configuration the broadcast messages received by this interface will be sent to the relay address. The interface configured with IP helper address should support broadcast mode. An interface can be configured with up to 20 relay addresses.

Perform the following task in Ethernet interface view.

Table 380 Configure interface relay address

Operation	Command
Configure interface relay address	ip relay-address ip-address
Delete interface relay address	undo ip relay-address [
	ip-address ]

By default, an interface has no IP address.

2Configure transparent transmission forwarding protocol