Cisco Catalyst 3750-X User Manual

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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 24 Configuring DHCP Features and IP Source Guard
Configuring DHCP Features
To disable DHCP snooping, use the no ip dhcp snooping global configuration command. To disable
DHCP snooping on a VLAN or range of VLANs, use the no ip dhcp snooping vlan vlan-range global
configuration command. To disable the insertion and removal of the option-82 field, use the no ip dhcp
snooping information option global configuration command. To configure an aggregation switch to
drop incoming DHCP snooping packets with option-82 information from an edge switch, use the no ip
dhcp snooping information option allow-untrusted global configuration command.
Step 6
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.
Step 7
interface interface-id Specify the interface to be configured, and enter interface configuration
mode.
Step 8
ip dhcp snooping vlan vlan information
option format-type circuit-id
[override] string ASCII-string
(Optional) Configure the circuit-ID suboption for the specified interface.
Specify the VLAN and port identifier, usi
ng a VLAN ID in the range of 1
to 4094. The default circuit ID is the port identifier, in the format
vlan-mod-port.
You can configure the circuit ID to be a string of 3 to 63 ASCII characters
(no spac
es).
(Optional) Use the o
verride keyword when you do not want the
circuit-ID suboption inserted in TLV format to define subscriber
information.
Step 9
ip dhcp snooping trust (Optional) Configure the interface as trusted or untrusted. Use the no
keyword to configure an interface to receive messages from an untrusted
client. The default setting is untrusted.
Step 10
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 with DHCP
snooping.
Step 11
exit Return to global configuration mode.
Step 12
ip dhcp snooping verify mac-address (Optional) Configure the switch to verify that the source MAC address in
a DHCP packet received on untrusted ports matches the client hardware
address in the packet. The default is to verify that the source MAC
address matches the client hardware address in the packet.
Step 13
end Return to privileged EXEC mode.
Step 14
show running-config Verify your entries.
Step 15
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose

Cisco Catalyst 3750-X Specifications

General

Switching Capacity	160 Gbps
Stacking Bandwidth	64 Gbps
Max Stacking Units	9
Layer Support	Layer 2 and Layer 3
Form Factor	Rack-mountable
DRAM	256 MB
Flash Memory	64 MB
Model	Cisco Catalyst 3750-X Series
Ports	24 or 48 10/100/1000 Ethernet ports
Uplink Interfaces	4 SFP or 2 SFP+
Features	StackWise Plus, EnergyWise
Image	IP Base or IP Services
Operating Temperature	0 to 40°C
Operating Humidity	10 to 85% noncondensing