Table of Contents
Advertisement
◆
E
This example enables the DHCP Snooping Information Option.
This command sets the DHCP snooping information option policy for DHCP
ip dhcp snooping
client packets that include Option 82 information.
information policy
S
D
replace
C
Global Configuration
C
When the switch receives DHCP packets from clients that already include
DHCP Option 82 information, the switch can be configured to set the action
just their MAC address. DHCP client-server exchange messages are
then forwarded directly between the server and client without having to
flood them to the entire VLAN.
DHCP snooping must be enabled for the DHCP Option 82 information to
be inserted into packets. When enabled, the switch will only add/
remove option 82 information in incoming DCHP packets but not relay
them. Packets are processed as follows:
If an incoming packet is a DHCP request packet with option 82
■
information, it will modify the option 82 information according to
settings specified with
command.
If an incoming packet is a DHCP request packet without option 82
■
information, enabling the DHCP snooping information option will
add option 82 information to the packet.
If an incoming packet is a DHCP reply packet with option 82
■
information, enabling the DHCP snooping information option will
remove option 82 information from the packet.
XAMPLE
Console(config)#ip dhcp snooping information option
Console(config)#
YNTAX
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.
S
EFAULT
ETTING
M
OMMAND
ODE
U
OMMAND
SAGE
– 1119 –
| General Security Measures
C
29
HAPTER
ip dhcp snooping information policy
DHCPv4 Snooping
Advertisement
Chapters
Table of Contents
