Configuring Option 82

For information on Option 82, see the sections beginning with DHCP Option 82.

To configure DHCP Option 82 on a routing switch, enter the dhcp-relay option 82 command.

Syntax:


dhcp-relay option 82 <append[validate]|replace[validate]|drop[validate]|keep> [ip|mac|mgmt-vlan]

`append`	Configures the switch to append an Option 82 field to the client DHCP packet. If the client packet has existing Option 82 field(s) assigned by another device, the new field is appended to the existing fields.The appended Option 82 field includes the switch Circuit ID (inbound port number*) associated with the client DHCP packet, and the switch Remote ID. The default switch remote ID is the MAC address of the switch on which the packet was received from the client. To use the incoming VLAN’s IP address or the Management VLAN IP address (if configured) for the remote ID instead of the switch MAC address, use the `ip` or `mgmt-vlan` option (below).
`replace`	Configures the switch to replace existing Option 82 fields in an inbound client DHCP packet with an Option 82 field for the switch.The replacement Option 82 field includes the switch circuit ID (inbound port number*) associated with the client DHCP packet and the switch remote ID. The default switch remote ID is the MAC address of the switch on which the packet was received from the client.To use the incoming VLAN's IP address or the Management VLAN IP address (if configured) for the remote ID instead of the switch MAC address, use the `ip` or `mgmt-vlan` option (below).
`drop`	Configures the routing switch to unconditionally drop any client DHCP packet received with existing Option 82 fields. This means that such packets will not be forwarded. Use this option where access to the routing switch by untrusted clients is possible.If the routing switch receives a client DHCP packet without an Option 82 field, it adds an Option 82 field to the client and forwards the packet. The added Option 82 field includes the switch circuit ID (inbound port number*) associated with the client DHCP packet and the switch remote ID. The default switch remote ID is the MAC address of the switch on which the packet was received from the client.To use the incoming VLAN's IP address or the Management VLAN IP address (if configured) for the remote ID instead of the switch MAC address, use the `ip` or `mgmt-vlan` option (below).
`keep`	For any client DHCP packet received with existing Option 82 fields, configures the routing switch to forward the packet as-is, without replacing or adding to the existing Option 82 fields.
`[validate]`	Operates when the routing switch is configured with append, replace, or drop as a forwarding policy. With `validate` enabled, the routing switch applies stricter rules to an incoming Option 82 server response to determine whether to forward or drop the response. For more information, see Validation of server response packets.
`[ip \| mac \| mgmt-vlan]`	Specifies the remote ID suboption that the switch uses in Option 82 fields added or appended to DHCP client packets. The type of remote ID defines DHCP policy areas in the client requests sent to the DHCP server. If a remote ID suboption is not configured, the routing switch defaults to the `mac` option. See Option 82 field content. `ip:` Specifies the IP address of the VLAN on which the client DHCP packet enters the switch. `mac:` Specifies the routing switch's MAC address. (The MAC address used is the same MAC address that is assigned to all VLANs configured on the routing switch.) This is the default setting. `mgmt-vlan:` Specifies the IP address of the (optional) management VLAN configured on the routing switch. Requires that a management VLAN is already configured on the switch. If the management VLAN is multinetted, the primary IP address configured for the management VLAN is used for the remote ID. If you enter the `dhcp-relay option 82` command without specifying either `ip` or `mac`, the MAC address of the switch on which the packet was received from the client is configured as the remote ID. For information about the remote ID values used in the Option 82 field appended to client requests, see Option 82 field content.