180
MES1000, MES2000 Ethernet Switches
information (device name, port number), added by the switch working in DHCP Relay agent mode, in the
form of DHCP request, received from the client. According to this option, DHCP server issues IP address (IP
address range) and other parameters to the switch port. When the necessary data is received from the
server, DHCP Relay agent issues IP address and send other necessary data to the client.
In order to use Option 82, the device should have DHCP relay agent function enabled. To
enable DHCP relay agent function, use 'ip dhcp relay enable' command in the global
configuration mode (see the respective section of the operation manual).
To ensure the correct operation of DHCP snooping feature, all utilized DHCP servers should
be connected to trusted switch ports. To add port into the trusted port list, use 'ip dhcp
snooping trust' command in the interface configuration mode. To ensure proper protection,
all other switch ports should be deemed as 'untrusted'.
Global configuration mode commands
Command line request in global configuration mode appears as follows:
console(config)#
Table 5.209 —Global configuration mode commands
Command
Value/Default value
Action
ip dhcp snooping
DHCP protocol
management is enabled by
default.
Enable DHCP protocol management for the switch.
no ip dhcp snooping
Disable DHCP protocol management for the switch.
ip dhcp snooping vlan
vlan_id
vlan_id: 1..4094
DHCP protocol
management is enabled by
default.
Enable DHCP protocol management in the scope of specific
VLAN.
no ip dhcp snooping vlan
vlan_id
Disable DHCP protocol management in the scope of specific
VLAN.
ip dhcp snooping
information option
allowed-untrusted
By default, reception of
DHCP packets with Option
82 from untrusted ports is
disabled.
Allow to receive DHCP packets with Option 82 from untrusted
ports.
no ip dhcp snooping
information option
allowed-untrusted
Deny to receive DHCP packets with Option 82 from untrusted
ports.
ip dhcp snooping verify
Verification is enabled by
default.
Enable verification of client and source MAC addresses,
received in DHCP packet from the untrusted port.
no ip dhcp snooping verify
Disable verification of client and source MAC addresses,
received in DHCP packet from the untrusted port.
ip dhcp snooping database
Backup file is not used
Allow DHCP management backup file (database) usage.
no ip dhcp snooping
database
Deny DHCP management backup file (database) usage.
ip dhcp snooping database
update-freq
seconds
(600 – 86400)/1200
Define DHCP management file (database) update rate.
no ip dhcp snooping
database update-freq
seconds
Restore the default value.
ip dhcp information option
Adding Option 82 is
enabled by default.
Allow the device to add Option 82 in DHCP operation.
no ip dhcp information
option
Deny the device to add Option 82 in DHCP operation.
ip dhcp information option
format-type access-node-id
node_id
node_id: 1..32 characters
Specify the access-node_id identifier of option 82.
no ip dhcp information
option format-type access-
node-id
Set the default value.
ip dhcp information option
format-type remote-id
remote_id: (1..32)
characters/-
Specifies the Option 82 remote_id identifier.