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Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter22 Configuring DHCP Features and IP Source Guard Features
Configuring DHCP Snooping
To remove the DHCP packet forwarding address, use the no ip helper-address address interface
configuration command.
Enabling DHCP Snooping and Option 82
Beginning in privileged EXEC mode, follow these steps to enable DHCP snooping on the switch:
Step10 show running-config Verify your entries.
Step11 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 ip dhcp snooping Enable DHCP snooping globally.
Step3 ip dhcp snooping vlan vlan-range Enable DHCP snooping on a VLAN or range of VLANs. The range is
1 to 4094.
You can enter a single VLAN ID identified by VLAN ID number, a series
of VLAN IDs separated by commas, a range of VLAN IDs separated by
hyphens, or a range of VLAN IDs separated by entering the starting and
ending VLAN IDs separated by a space.
Step4 ip dhcp snooping information option Enable the switch to insert and to remove DHCP relay information
(option-82 field) in forwarded DHCP request messages to the DHCP
server. This is the default setting.
Step5 ip dhcp snooping information option
format remote-id [string ASCII-string |
hostname]
(Optional) Configure the remote-ID suboption.
You can configure the remote ID as
String of up to 63 ASCII characters (no spaces)
Configured hostname for the switch
Note If the hostname is longer than 63 characters, it is truncated to 63
characters in the remote-ID configuration.
The default remote ID is the switch MAC address.
Step6 ip dhcp snooping information option
allow-untrusted
(Optional) If the switch is an aggregation switch connected to an edge
switch, enable the switch to accept incoming DHCP snooping packets
with option-82 information from the edge switch.
The default setting is disabled.
Note Enter this command only on aggregation switches that are
connected to trusted devices.
Step7 interface interface-id Specify the interface to be configured, and enter interface configuration
mode.