Configuring the DHCP Relay Agent Option 82 Settings

Configuring Relay Agent Option 82 Information

You can specify the type the relay agent option 82 information that the router adds to DHCP packets before it relays the packets to the DHCP server. You can use one of the following keywords to add either the hostname or virtual router name to the front of the Circuit-Id field or to strip the subinterface ID from the Interface-Id field:

• hostname—Adds the router’s hostname to the front of the Circuit-Id field; a colon separates the hostname from the circuit information
• vrname—Adds the router’s virtual router name to the front of the Circuit-Id field; a colon separates the virtual router name from the circuit information
• Use the exclude-subinterface-id to strip the subinterface ID from the Interface-Id field. When the interface ID is constructed, it contains the slot/port numbers, the subinterface ID, and the VPI/VCI for ATM interfaces or the VLAN ID for Ethernet interfaces. Use this keyword to remove the subinterface ID from the Interface-Id field.

The hostname and vrname keywords are a toggle; that is, specifying either hostname or virtual router name turns off the other selection.

• To configure the relay agent option 82 information:
  host1(config)#set dhcp relay options hostname

Preventing Option 82 Information from Being Stripped from Trusted Client Packets

You can configure DHCP relay or DHCP relay proxy to preserve option 82 information for trusted clients. This ensures that DHCP relay and DHCP relay proxy prevent option 82 information from being stripped off packets destined for a trusted client. A trusted client has a giaddr value of 0. If DHCP relay is configured not to remove option 82 and the giaddr field is 0, option 82 information remains in the packets.

• To prevent the option 82 information from being removed from packets destined for a trusted client:
  host1(config)#set dhcp relay preserve-trusted-client-option

Configuring Relay Agent Information Option (Option 82) Suboption Values

The JunosE Software provides two commands that you can use to configure DHCP relay agent information suboptions.

• To configure option 82 to include any combination of the supported suboptions, including the Vendor-Specific suboption:
  host1(config)#set dhcp relay agent sub-option remote-id host1(config)#set dhcp relay agent sub-option circuit-id host1(config)#set dhcp relay agent sub-option vendor-specific layer2-circuit-id host1(config)#set dhcp relay agent sub-option vendor-specific user-packet-class

• To configure option 82 to include either or both the Agent Circuit ID suboption (suboption 1) and Agent Remote ID suboption (suboption 2). The command does not support the Vendor-Specific suboption (suboption 9).
  host1(config)#set dhcp relay agent