LevelOne GTL-2691 - Manual (Page 950)

C HAPTER 29 | General Security Measures
DHCP Snooping
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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 ip dhcp snooping information policy
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.
E XAMPLE
This example enables the DHCP Snooping Information Option.
Console(config)#ip dhcp snooping information option
Console(config)#
ip dhcp snooping
information policy
This command sets the DHCP snooping information option policy for DHCP
client packets that include Option 82 information.
S 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.
D EFAULT S ETTING
replace
C OMMAND M ODE
Global Configuration
C OMMAND U SAGE
When the switch receives DHCP packets from clients that already include
DHCP Option 82 information, the switch can be configured to set the action