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User’s Manual of SGSD-1022 / SGSD-1022P
SGSW-2840 / SGSW-2840P
490
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.
Example
This
Example enables MAC address verification.
Console(config)#ip dhcp snooping verify mac-address
Console(config)#
Related Commands
ip dhcp snooping
ip dhcp snooping vlan
ip dhcp snooping trust
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.
Syntax
[no] ip dhcp snooping information option
Default Setting
Disabled
Command Mode
Global Configuration
Command Usage
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.
DHCP request packets are flooded onto all attached VLANs other than the inbound VLAN under the following situations:
-DHCP snooping is disabled. -The request packet contains a valid relay agent address field.
• DHCP reply packets are flooded onto all attached VLANs other than the inbound management VLAN under the following
situations: -The reply packet does not contain Option 82 information. -The reply packet contains a valid relay agent
address field (that is not the
address of this switch) or a zero relay address.