This topic describes how to configure the DHCP relay agent information option on the Cisco 8000 Series Router.
A DHCP relay agent may receive a message from another DHCP relay agent that already contains relay information. By default, the relay information from the previous relay agent is replaced (using the replace option).
Procedure
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Enter the DHCP IPv4 configuration submode.
Example:
Router# configure Router(config)# dhcp ipv4 -
Enter the DHCP IPv4 profile relay submode.
Example:
Router(config-dhcpv4)# profile RELAY relay -
Configure the system to insert the DHCP relay agent information option (option-82 field) in forwarded BOOTREQUEST messages to a DHCP server.
Note
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This option is injected by the relay agent while forwarding client-originated DHCP packets to the server. Servers recognizing this option can use the information to implement IP address or other parameter assignment policies. When replying, the DHCP server echoes the option back to the relay agent. The relay agent removes the option before forwarding the reply to the client.
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The relay agent information is organized as a single DHCP option that contains one or more suboptions. These options contain the information known by the relay agent. The supported suboptions are Remote ID and Circuit ID.
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This function is disabled by default. The port field of the default circuit-ID denotes the configured bundle-ID of the bundle. If circuit IDs require that bundles be unique, and because the port field is 8 bits, the low-order 8 bits of configured bundle IDs must be unique. To achieve this, configure bundle IDs within the range from 0 to 255.
Example:
Router(config-dhcpv4-relay-profile)# relay information option -
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(Optional) Configure DHCP to check the validity of the relay agent information option in forwarded BOOTREPLY messages.
Note
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If an invalid message is received, the relay agent drops the message. If a valid message is received, the relay agent removes the relay agent information option field and forwards the packet.
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By default, DHCP does not check the validity of the relay agent information option field in DHCP reply packets received from the DHCP server.
Example:
Router(config-dhcpv4-relay-profile)# relay information check -
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(Optional) Configure the reforwarding policy for the DHCP relay agent. That is, whether the relay agent drops or keeps the relay information.
Note
By default, the DHCP relay agent replaces the relay information option.
Example:
Router(config)# dhcp ipv4 profile TEST relay relay information policy drop Router(config)# commit