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Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-08
Chapter 22 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.
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
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, using 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 spaces).
(Optional) Use the
override
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
Содержание Catalyst 3750-E Series
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