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Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 37 Configuring DHCP Snooping
Configuring DHCP Snooping
Configuring DHCP Snooping Rate Limiting on Layer 2 LAN Interfaces
To configure DHCP snooping rate limiting on a Layer 2 LAN interface, perform this task:
When configuring DHCP snooping rate limiting on a Layer 2 LAN interface, note the following
information:
•
We recommend an untrusted rate limit of not more than 100 packets per second (pps).
•
If you configure rate limiting for trusted interfaces, you might need to increase the rate limit on trunk
ports carrying more than one VLAN on which DHCP snooping is enabled.
•
DHCP snooping puts ports where the rate limit is exceeded into the error-disabled state.
This example shows how to configure DHCP packet rate limiting to 100 pps on Fast Ethernet port 5/12:
Router#
configure terminal
Router(config)#
interface FastEthernet 5/12
Router(config-if)#
ip dhcp snooping limit rate 100
Router(config-if)#
do show ip dhcp snooping | begin pps
Interface Trusted Rate limit (pps)
------------------------ ------- ----------------
FastEthernet5/12 no 100
Router#
Configuring the DHCP Snooping Database Agent
To configure the DHCP snooping database agent, perform one or more of the following tasks:
Command
Purpose
Step 1
Router(config)#
interface
{
type
1
slot/port
|
port-channel
number
}
1.
type
=
ethernet
,
fastethernet
,
gigabitethernet
, or
tengigabitethernet
Selects the interface to configure.
Note
Select only LAN ports configured with the
switchport
command or Layer 2 port-channel
interfaces.
Step 2
Router(config-if)#
ip dhcp snooping limit rate
rate
Configures DHCP packet rate limiting.
Step 3
Router(config-if)#
no ip dhcp snooping limit rate
Disables DHCP packet rate limiting.
Step 4
Router(config-if)#
do show ip dhcp snooping |
begin pps
Verifies the configuration.
Command
Purpose
Router(config)#
ip dhcp snooping database
{
_url
|
write-delay
seconds
|
timeout
seconds
}
(Required) Configures a URL for the database agent (or file)
and the related timeout values.
Router(config)#
no ip dhcp snooping database
[
write-delay
|
timeout
]
Clears the configuration.
Router#
show ip dhcp snooping database
[
detail
]
(Optional) Displays the current operating state of the
database agent and statistics associated with the transfers.
Router#
clear ip dhcp snooping database statistics
(Optional) Clears the statistics associated with the database
agent.