HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 3 - IP Services Conf - Page 43

Figure 29 DHCP relay agent work process 1. After receiving a DHCP-DISCOVER or DHCP-REQUEST broadcast message from a DHCP client, the DHCP relay agent fills the giaddr field of the message with its IP address and forwards the message to the designated DHCP server in unicast mode. 2. Based on the giaddr field, the DHCP server returns an IP address and other configuration parameters to the relay agent, and the relay agent conveys them to the client. DHCP relay agent support for Option 82 Option 82 records location information of the DHCP client, letting the administrator locate the DHCP client for security control and accounting purposes. For more information, see "DHCP overview." If the DHCP relay agent supports Option 82, it handles a client's request according to the contents defined in Option 82, if any. The handling strategies are described in Table 2. If a reply returned by the DHCP server contains Option 82, the DHCP relay agent removes the Option 82 before forwarding the reply to the client. Table 2 Handling strategies of the DHCP relay agent If a client's requesting message has... Handling strategy Drop Keep Option 82 Replace no Option 82 N/A Padding format The DHCP relay agent will... Random Random normal verbose user-defined normal Drop the message. Forward the message without changing Option 82. Forward the message after replacing the original Option 82 with the Option 82 padded in normal format. Forward the message after replacing the original Option 82 with the Option 82 padded in verbose format. Forward the message after replacing the original Option 82 with the user-defined Option 82. Forward the message after adding the Option 82 padded in normal format. 35