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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 gigabitethernet0/1
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:
Command
Step 1
configure terminal
Step 2
ip dhcp snooping database
{flash:/filename |
ftp://user:password@host/filename |
http://[[username:password]@]{hostna
me | host-ip}[/directory]
/image-name.tar |
rcp://user@host/filename}|
tftp://host/filename
Step 3
ip dhcp snooping database timeout
seconds
Step 4
ip dhcp snooping database write-delay
seconds
Step 5
end
Step 6
ip dhcp snooping binding mac-address
vlan vlan-id ip-address interface
interface-id expiry seconds
Catalyst 2928 Switch Software Configuration Guide
19-12
Chapter 19
Purpose
Enter global configuration mode.
Specify the URL for the database agent or the binding file by using one
of these forms:
flash:/filename
•
ftp://user:password@host/filename
•
http://[[username:password]@]{hostname | host-ip}[/directory]
•
/image-name.tar
rcp://user@host/filename
•
tftp://host/filename
•
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.
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).
Return to privileged EXEC mode.
(Optional) Add binding entries to the DHCP snooping binding database.
The vlan-id range is from 1 to 4904. The seconds range is from
1 to 4294967295.
Enter this command for each entry that you add.
Note
Use this command when you are testing or debugging the switch.
Configuring DHCP Features and IP Source Guard Features
OL-23389-01
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Troubleshooting
