Ip Dhcp Snooping Information Option Allow-Untrusted - Cisco 220 Series Smart Plus Reference Manual

IP DHCP Snooping Commands

ip dhcp snooping information option allow-untrusted

ip dhcp snooping information option allow-untrusted
Cisco 220 Series Smart Plus Switches Command Line Interface Reference Guide Release 1.0.0.x
When the option-82 feature is enabled and a switch receives a DHCP request from
a host, it adds the option-82 information in the packet. The option-82 information
contains the switch MAC address (the remote ID suboption) and the port identifier,
vlan-mod-port, from which the packet is received (circuit ID suboption). The switch
forwards the DHCP request that includes the option-82 field to the DHCP server.
When the DHCP server receives the packet, it can use the remote ID, the circuit ID,
or both to assign IP addresses and implement policies, such as restricting the
number of IP addresses that can be assigned to a single remote ID or a circuit ID.
The DHCP server then echoes the option-82 field in the DHCP reply.
The DHCP server unicasts the reply to the switch if the request was relayed to the
server by the switch. When both the client and server are on the same subnet, the
server broadcasts the reply. The switch inspects the remote ID and possibly the
circuit ID fields to verify that it originally inserted the option-82 data. The switch
removes the option-82 field and forwards the packet to the switch port that
connects to the DHCP host that sends the DHCP request.
Example
switchxxxxxx(config)# ip dhcp snooping information option
switchxxxxxx(config)# ip dhcp snooping information option format remote-id
test
To configure an aggregation switch to accept DHCP packets with option-82
information which are received on the untrusted ports that might be connected to
an edge switch, use the ip dhcp snooping information option allow-untrusted
Interface Configuration mode command.
To configure the switch to drop these packets from the edge switch, use the no
form of this command.
Syntax
ip dhcp snooping information option allow-untrusted [replace]
no ip dhcp snooping information option allow-untrusted
Parameters
• replace—(Optional) Replaces DHCP packets with option-82 information.
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