Purpose
Command or Action
Configures multiple physical ports that are connected to the DHCP
clients, and enter interface range configuration mode.
interface range port-range
or
interface
interface-id
Step 6
Example:
Switch(config)# interface
gigabitethernet1/0/2
or
Configures a single physical port that is connected to the DHCP
client, and enter interface configuration mode.
Defines the VLAN membership mode for the port.
switchport mode access
Example:
Switch(config-if)# switchport mode access
Step 7
Assigns the ports to the same VLAN as configured in Step 2.
switchport access vlan vlan-id
Example:
Switch(config-if)# switchport access vlan
1
Step 8
Returns to privileged EXEC mode.
end
Example:
Switch(config-if)# end
Step 9
Prerequisites for Configuring DHCP Snooping and Option 82
The prerequisites for DHCP Snooping and Option 82 are as follows:
•
Before configuring the DHCP snooping information option on your switch, be sure to configure the
device that is acting as the DHCP server. You must specify the IP addresses that the DHCP server can
assign or exclude, or you must configure DHCP options for these devices.
•
For DHCP snooping to function properly, all DHCP servers must be connected to the switch through
trusted interfaces.
•
Before configuring the DHCP relay agent on your switch, make sure to configure the device that is
acting as the DHCP server. You must specify the IP addresses that the DHCP server can assign or
exclude, configure DHCP options for devices, or set up the DHCP database agent.
•
The following prerequisites apply to DHCP snooping binding database configuration:
◦
Because both NVRAM and the flash memory have limited storage capacity, we recommend that
you store the binding file on a TFTP server.
◦
For network-based URLs (such as TFTP and FTP), you must create an empty file at the configured
URL before the switch can write bindings to the binding file at that URL. See the documentation
for your TFTP server to determine whether you must first create an empty file on the server; some
TFTP servers cannot be configured this way.
Catalyst 2960-XR Switch Security Configuration Guide, Cisco IOS Release 15.0(2)EX1
176
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Configuring DHCP
Prerequisites for Configuring DHCP Snooping and Option 82