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    Using the set dhcp relay agent sub-option Command to Enable Option 82 Suboption Support

    Note: We recommend that you use the set dhcp relay agent sub-option command for new option 82 suboption configurations. However, JunosE Software continues to support the set dhcp relay agent command, with option 82 suboptions, to provide backward-compatibility for existing scripts.

    You use the set dhcp relay agent sub-option command to enable support for a specific DHCP relay agent option 82 suboption—Agent Circuit ID (suboption 1), Agent Remote ID (suboption 2), and Vendor-Specific (suboption 9). When you issue this command, the router adds DHCP relay agent information suboption 1 to every packet it relays from a DHCP client to a DHCP server. The Agent Circuit ID suboption identifies the interface on which DHCP packets are received. When the packets are received on a LAG interface, the router clearly identifies the interface.

    The suboptions include information from the DHCP relay agent that the DHCP server can use to implement parameter assignment policies. The DHCP server echoes the suboptions when it replies to the DHCP client, but the DHCP relay strips the suboptions before relaying the packets to the client.

    The Agent Circuit ID suboption identifies the interface on which the DHCP packets are received. This suboption contains the following information, based on interface type:

    • ATM interface
      [<hostname>|<vrname>:]<interface type> <slot>/<port>[.<sub-if>]:<vpi>.<vci>


      atm 4/1.2:0.101relayVr:atm 4/1:0.101bostonHost:atm 4/1.2:0.101
    • Ethernet interface
      [<hostname>|<vrname>:]<interface type> <slot>/<port>


      fastEthernet 1/2relayVr:fastEthernet 1/2bostonHost:fastEthernet 1/2
    • Ethernet interface with VLAN
      [<hostname>|<vrname>:]<interface type> <slot>/<port>[.<sub-if>]:<vlan id>


      fastEthernet 1/2.3:4relayVr:fastEthernet 1/2:4bostonHost:fastEthernet 1/2.3:4
    • Ethernet interface with Stacked VLAN
      [<hostname>|<vrname>:]<interface type> <slot>/<port>[.<sub-if>]:
      <svlan id>-<vlan id>


      fastEthernet 1/2.3:4-5relayVr:fastEthernet 1/2:4-5bostonHost:fastEthernet 1/2.3:4-5
    • LAG interface
      [<hostname>|<vrname>:]<interface type> <bundle name>


      lag bundleArelayVr:lag bundleAbostonHost:lag bundleA
    • LAG interface with VLAN
      [<hostname>|<vrname>:]<interface type> <bundle name>[.<sub-if>]:<vlan id>


      lag bundleA.1:2relayVr:lag bundleA:2bostonHost:lag bundleA.1:2
    • LAG interface with Stacked VLAN
      [<hostname>|<vrname>:]<interface type> <bundle name>[.<sub-if>]:
      <svlan id>-<vlan id>


      lag bundleA.1:2-3relayVr:lag bundleA:2-3bostonHost:lag bundleA.1:2-3

    The Agent Remote ID suboption contains a value only when (1) the interface is a dynamic ATM interface and (2) the subscriber command is used to configure a username and domain name for the interface. If both conditions are met, the suboption contains a string with the username and domain name in the format: username@domainname.

    The Vendor-Specific suboption contains a value that includes a JunosE data field. You can configure the data field to support one or both of the following values:

    • layer2-circuit-id (type 1)—The hexadecimal representation of the layer 2 identifier in the Agent Circuit ID (suboption 1) value (for example, the ATM VPI/VCI or Ethernet SVLAN/VLAN ID). You can configure this suboption type without the Agent Circuit ID.
    • user-packet-class (type 2)—The hexadecimal representation of the user packet class field, whose value is assigned by the layer 2 policy application. The layer 2 policy application can be used to map the DHCP packet or message IEEE 802.1p value to the user packet class field. See the JunosE Policy Management Configuration Guide for information about layer 2 policies.

    Published: 2014-08-20