Brocade 6910 Ethernet Access Switch Configuration Guide (Supporting R2.2.0.0) User Manual
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Brocade 6910 Ethernet Access Switch Configuration Guide
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DHCP Snooping
Default Setting
Option 82: Disabled
CID/RID sub-type: Enabled
Remote ID: MAC address (hexadecimal)
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 82 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.
•
When the DHCP Snooping Information Option is enabled, clients can be identified 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 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.
Example
This example enables the DHCP Snooping Information Option.
Console(config)#ip dhcp snooping information option
Console(config)#