SignaMax SC30010, Справочное руководство CLI

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Chapter 9
| General Security Measures
DHCPv4 Snooping
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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 DHCP 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.
Example
This example enables the DHCP Snooping Information Option.
Console(config)#ip dhcp snooping information option
Console(config)#