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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-06
Chapter 19 Configuring DHCP Features and IP Source Guard
Configuring DHCP Features
Step 3 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.
Step 4 ip dhcp snooping information option Enable the switch to insert and remove DHCP relay information
(option-82 field) in forwarded DHCP request messages to the DHCP
server. This is the default setting.
Step 5 ip dhcp snooping information option
format remote-id [string ASCII-string |
hostname]
(Optional) Configure the remote-ID suboption.
You can configure the remote ID to be:
• 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.
Step 6 ip dhcp snooping information option
allowed-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 is disabled.
Note You must enter this command only on aggregation switches that
are connected to trusted devices.
Step 7 interface interface-id Specify the interface to be configured, and enter interface configuration
mode.
Step 8 no shutdown Enable the port, if necessary. By default, UNIs and ENIs are disabled and
NNIs are enabled.
Step 9 ip dhcp snooping vlan vlan information
option format-type circuit-id string
ASCII-string
(Optional) Configure the circuit-ID suboption for the specified interface.
Specify the VLAN and port identifier, using a VLAN ID in the range of 1
to 4094.
You can configure the circuit ID to be a string of 3 to 63 ASCII characters
(no spaces).
The default circuit ID is the port identifier, in the format vlan-mod-port.
Step 10 ip dhcp snooping trust (Optional) Configure the interface as trusted or untrusted. You can use the
no keyword to configure an interface to receive messages from an
untrusted client. The default is untrusted.
Step 11 ip dhcp snooping limit rate rate (Optional) Configure the number of DHCP packets per second that an
interface can receive. The range is 1 to 2048. By default, no rate limit is
configured.
Note We recommend an untrusted rate limit of not more than 100
packets per second. If you configure rate limiting for trusted
interfaces, you might need to increase the rate limit if the port is
a trunk port assigned to more than one VLAN on which DHCP
snooping is enabled.
Command Purpose