C
HAPTER
24
| General Security Measures
DHCP Snooping
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ip dhcp snooping
information policy
This command sets the DHCP snooping information option policy for DHCP
client packets that include Option 82 information.
SYNTAX
ip dhcp snooping information policy {drop | keep | replace}
drop - Drops the client’s request packet instead of relaying it.
keep - Retains the Option 82 information in the client request, and
forwards the packets to trusted ports.
replace - Replaces the Option 82 information circuit-id and
remote-id fields in the client’s request with information about the
relay agent itself, inserts the relay agent’s address (when DHCP
snooping is enabled), and forwards the packets to trusted ports.
DEFAULT SETTING
replace
COMMAND MODE
Global Configuration
COMMAND USAGE
When the switch receives DHCP packets from clients that already include
DHCP Option 82 information, the switch can be configured to set the action
policy for these packets. The switch can either drop the DHCP packets,
keep the existing information, or replace it with the switch’s relay
information.
EXAMPLE
Console(config)#ip dhcp snooping information policy drop
Console(config)#
ip dhcp snooping
verify mac-address
This command verifies the client’s hardware address stored in the DHCP
packet against the source MAC address in the Ethernet header. Use the no
form to disable this function.
SYNTAX
[no] ip dhcp binding verify mac-address
DEFAULT SETTING
Enabled
COMMAND MODE
Global Configuration
COMMAND USAGE
If MAC address verification is enabled, and the source MAC address in the
Ethernet header of the packet is not same as the client’s hardware address
in the DHCP packet, the packet is dropped.
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