For information on configuring an Option 82 DHCP server, see the documentation provided with the server application.

The DHCP relay agent transfers DHCP messages from DHCP clients located on a subnet without a DHCP server to other subnets.

Neither side is aware of the communications that pass through the DHCP relay agent.

As DHCP clients broadcast requests, the DHCP relay agent receives the packets and forwards them to the DHCP server.

During this process, the DHCP relay agent increases the hop count by one before forwarding the DHCP message to the server.

The DHCP relay agent sets the destination IP address of the packet to the IP address of the DHCP server and forwards the message.

However, if DHCP has been disabled, you can re-enable it by entering the following command at the global configuration level.

The command must be executed from the global configuration level.

It is added in the hpicfDhcpclient.mib.

The hostname is retrieved from the MIB variable SYSNAME.

If SYSNAME is more than 30 characters, then DHCP Option 12 will not be included in the packet.

If the SYSNAME in the MIB is null, then DHCP Option 12 will not be included in the packet.

The helper addresses are shared between the DHCP relay agent and UDP forwarder feature.

Servers recognizing the relay agent information option may use the information to implement IP address or other parameter assignment policies.

The DHCP server echoes the option back verbatim to the relay agent in server-to-client replies, and the relay agent strips the option before forwarding the reply to the client.

The initial suboptions are defined for a relay agent that is co-located in a public circuit access unit.

These include a circuit ID for the incoming circuit and a remote ID that provides a trusted identifier for the remote high-speed modem.

Without Option 82, DHCP operation modifies client IP address request packets to the extent needed to forward the packets to a DHCP server.

Option 82 enhances this operation by enabling the routing switch to append an Option 82 field to such client requests.

This field includes two suboptions for identifying the routing switch (by MAC address or IP address) and the routing switch port the client is using to access the network.

A DHCP server with Option 82 capability can read the appended field and use this data as criteria for selecting the IP addressing it will return to the client through the usual DHCP server response packet.

This operation provides several advantages over DHCP without Option 82.

DHCP servers that are not compliant with Option 82 operation ignore Option 82 fields.

Ip Helper Address