CLI Reference Guide-R07

Table Of Contents
Chapter 26
| DHCP Commands (IPv4 and IPv6)
DHCP Relay (IPv4 and IPv6)
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Proxy ARP is disabled
DHCP Client Vendor Class ID (text): ECS4510-28T
DHCP Relay Server:
Console#
Related Commands
ip dhcp relay server (635)
ip dhcp relay
information option
This command enables DHCP Option 82 information relay. Use the no form of this
command to disable this feature.
Syntax
[no] ip dhcp relay information option
Default Setting
Option 82: Disabled
Command Mode
Global Configuration
Usage Guidelines
Using this command will enable DHCP Option 82 information relay. You must
also specify the IP address for at least one active DHCP server (with the ip dhcp
relay server command). Otherwise, the switchs DHCP relay agent will not be
able to forward client requests to a DHCP server.
DHCP provides a relay agent information option for sending information about
its DHCP clients or the relay agent itself to the DHCP server. Also known as
DHCP Option 82, it allows compatible DHCP servers to use this information
when assigning IP addresses, or to set other services or policies for clients.
When Option 82 is enabled, the requesting client (or an intermediate relay
agent that has used the information fields to describe itself) can be identified in
the DHCP request packets forwarded by the switch and in reply packets sent
back from the DHCP server. This information may specify the MAC address, IP
address, or an arbitrary string for the requesting device (that is, the relay agent
in this context).
The relay agent will fill in the Option 82 circuit-id field with information
indicating the local interface over which the switch received the DHCP client
request, including the VLAN ID, stack unit, and port. This allows DHCP client-
server exchange messages to be forwarded between the server and client
without having to flood them onto the entire VLAN.
DHCP request packets received by the switch are handled as follows: