SNR S2989G-8TX [209/553] Dhcp option 82 configuration task list

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S2989G-24TX Operation Manual

Chapter 3 IP services Configuration

3-47

DHCPRelayAgent

DHCP Request DHCP Request Option82

DHCP Reply

DHCP Reply Option82

DHCP Client

DHCP Server

Figure 3-12 DHCP option 82 flow chart

If the DHCP Relay Agent supports option 82, the DHCP client should go through the

following four steps to get its IP address from the DHCP server: discover, offer, select and

acknowledge. The DHCP protocol follows the procedure below:

1） DHCP client sends a request broadcast message while initializing. This request

message does not have option 82.

2） DHCP Relay Agent will add the option 82 to the end of the request message it

receives, then relay and forward the message to the DHCP server. By default, the sub-

option 1 of option 82 (Circuit ID) is the interface information of the switch connected to

the DHCP client (VLAN name and physical port name), but the users can configure the

Circuit ID as they wish. The sub-option 2 of option 82(Remote ID) is the MAC address of

the DHCP relay device.

3） After receiving the DHCP request message, the DHCP server will allocate IP address

and other information for the client according to the information and preconfigured policy

in the option segment of the message. Then it will forward the reply message with DHCP

configuration information and option 82 information to DHCP Relay Agent.

4） DHCP Relay Agent will peel the option 82 information from the replay message sent by

DHCP server, and then forward the message with DHCP configuration information to the

DHCP client.

3.15.2

DHCP option 82 Configuration Task List

1. Enabling the DHCP option 82 of the Relay Agent

2. Configure the DHCP option 82 attributes of the interface

3. Enable the DHCP option 82 of server

4. Configure DHCP option 82 default format of Relay Agent

5. Configure delimiter