Cisco CATALYST 2960 User Manual

20-11
Catalyst 2960 and 2960-S Switches Software Configuration Guide, Release 15.0(1)SE
OL-26520-01
Chapter 20 Configuring DHCP and IP Source Guard Features
Configuring DHCP Snooping
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 the 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.
This example shows how to enable DHCP snooping globally and on VLAN 10 and to configure a rate
limit of 100 packets per second on a port:
Switch(config)# ip dhcp snooping
Switch(config)# ip dhcp snooping vlan 10
Switch(config)# ip dhcp snooping information option
Switch(config)# interface gigabitethernet2/0/1
Switch(config-if)# ip dhcp snooping limit rate 100
Enabling the DHCP Snooping Binding Database Agent
Beginning in privileged EXEC mode, follow these steps to enable and configure the DHCP snooping
binding database agent on the switch:
Step 12
show running-config Verify your entries.
Step 13
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
ip dhcp snooping database
{flash[number]:/filename |
ftp://user:password@host/filename |
http://[[username:password]@]{hostna
me | host-ip}[/directory]
/image-name.tar |
rcp://user@host/filename}|
tftp://host/filename
Specify the URL for the database agent or the binding file by using one
of these forms:
• flash[number]:/filename
(Optional) Use the number parameter to specify the stack member
number of the stack master. The range for number is 1 to 4.
• ftp://user:password@host/filename
• http://[[username:password]@]{hostname | host-ip}[/directory]
/image-name.tar
• rcp://user@host/filename
• tftp://host/filename
Step 3
ip dhcp snooping database timeout
seconds
Specify (in seconds) how long to wait for the database transfer process to
finish before stopping the process.
The default is 300 seconds. The range is 0 to 86400. Use 0 to define an
infinite duration, which means to continue trying the transfer indefinitely.
Step 4
ip dhcp snooping database write-delay
seconds
Specify the duration for which the transfer should be delayed after the
binding database changes. The range is from 15 to 86400 seconds. The
default is 300 seconds (5 minutes).
Step 5
end Return to privileged EXEC mode.

Cisco CATALYST 2960 Specifications

General

Manageable	Yes
Stacking	No
Model	Catalyst 2960 Series Switches
Power over Ethernet (PoE)	Available on some models (IEEE 802.3af)
VLANs	255 active VLANs
Features	QoS
Operating Temperature	32 to 113°F (0 to 45°C)
Relative Humidity	10% to 85% non-condensing
Power Consumption	Varies by model (30W to 400W)