Microsens MS453490M Management Guide - Manual (Page 663)

C HAPTER 25 | General Security Measures
DHCP Snooping
– 663 –
ip dhcp snooping
database flash
This command writes all dynamically learned snooping entries to flash
memory.
C OMMAND M ODE
Privileged Exec
C OMMAND U SAGE
This command can be used to store the currently learned dynamic DHCP
snooping entries to flash memory. These entries will be restored to the
snooping table when the switch is reset. However, note that the lease time
shown for a dynamic entry that has been restored from flash memory will
no longer be valid.
E XAMPLE
Console(config)#ip dhcp snooping database flash
Console(config)#
ip dhcp snooping
information option
This command enables the DHCP Option 82 information relay for the
switch. Use the no form to disable this function.
S YNTAX
[no] ip dhcp snooping information option
D EFAULT S ETTING
Disabled
C OMMAND M ODE
Global Configuration
C OMMAND U SAGE
◆ DHCP provides a relay mechanism for sending information about the
switch and its DHCP clients to the DHCP server. Known as DHCP Option
82, it allows compatible DHCP servers to use the information when
assigning IP addresses, or to set other services or policies for clients.
◆ When the DHCP Snooping Information Option is enabled, the
requesting client (or an intermediate relay agent that has used the
information fields to describe itself) can be identified in the DHCP
request packets forwarded by the switch and in reply packets sent back
from the DHCP server by the switch port to which they are connected
rather than 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 on the switch for the DHCP Option 82
information to be inserted into packets.