SMC Networks 7724M/VSW - annexe 1, Manual

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Management Guide CLI
TigerAccess™ EE
SMC7824M/VSW 329
8.6.7.10 DHCP Snooping with Option82
In case of L2 environment, when forwarding DHCP messages to a DHCP server, a DHCP
switch can insert or remove DHCP option82 data on the DHCP messages from the clients.
In case of a switch is enabled with DHCP snooping, it floods DHCP packets with DHCP
option82 field when the DHCP option82 is enabled. This allows an enhanced security and
efficient IP assignment in the Layer 2 environment with a DHCP option82 field.
If DHCP snooping is enabled in the system of switch, DHCP packets includes DHCP op-
tion82 field by default.
To enable/disable the switch enabled by DHCP snooping to insert or remove DHCP op-
tion82 field, use the following command.
Command Mode Description
ip dhcp snooping information
option Enables the switch to insert DHCP option 82 field in
forwarded DHCP packets to the DHCP server.
no ip dhcp snooping informa-
tion option
Global
Disables the switch not to insert DHCP option 82 field
in forwarded DHCP packets to the DHCP server
8.6.7.11 DHCP Snooping Option
DHCP snooping switch may receive DHCP messages (Discover/Request) with various
different options from clients, which cause DHCP server hard to manage client’s inform-
tion in the perspective of data consistency. That’s why this function is necessay.
The switch operating DHCP snooping can modify or attach an option field of the DHCP
messages (Discover/Request) with a defined snooping option and can forward them to
DHCP server. The snooping option can be applied on a port basis or on entire ports. Be-
fore using this function, a global DHCP option format should be created. For details of
setting the DHCP option format, refer to the
8.6.5 DHCP Option .
To set a DHCP snooping option for a specifc port, use the following command.
Command Mode Description
ip dhcp snooping port PORTS
opt-code <1-254> format NAME
Specifies a snooping option format on a port.
opt-code: DHCP option code
NAME: DHCP option format name
ip dhcp snooping port PORTS
opt-code <1-254> policy { keep |
replace }
Configures a policy against DHCP option belonging to
a DHCP message (default: replace)
keep: forwards a DHCP message to DHCP server
without any modification.
replace: deletes the DHCP message’s option and adds
the snooping option if both of them are same. However,
if they are different each other,
replace option just
adds the snooping option.
no ip dhcp snooping port
PORTS opt-code
<1-254>
Global
Removes the DHCP snooping option for a given port.
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