• Configure an IP address and mask on the interface.
INTERFACE mode
ip address ip-address mask [secondary]
–ip-address mask: enter an address in dotted-decimal format (A.B.C.D). The mask must be in
slash format (/24).
–secondary: the IP address is the interface’s backup IP address. You can configure up to eight
secondary IP addresses.
Example of a Configuration for a VLAN Participating in an OSPF Process
interface Vlan 10
ip address 1.1.1.2/24
tagged TenGigabitEthernet 2/2-13
tagged TenGigabitEthernet 5/0
ip ospf authentication-key force10
ip ospf cost 1
ip ospf dead-interval 60
ip ospf hello-interval 15
no shutdown
!
Loopback Interfaces
A Loopback interface is a virtual interface in which the software emulates an interface. Packets routed to
it are processed locally.
Because this interface is not a physical interface, you can configure routing protocols on this interface to
provide protocol stability. You can place Loopback interfaces in default Layer 3 mode.
To configure, view, or delete a Loopback interface, use the following commands.
• Enter a number as the Loopback interface.
CONFIGURATION mode
interface loopback number
The range is from 0 to 16383.
• View Loopback interface configurations.
EXEC mode
show interface loopback number
• Delete a Loopback interface.
CONFIGURATION mode
no interface loopback number
Many of the commands supported on physical interfaces are also supported on a Loopback interface.
Null Interfaces
The Null interface is another virtual interface. There is only one Null interface. It is always up, but no
traffic is transmitted through this interface.
To enter INTERFACE mode of the Null interface, use the following command.
Interfaces 409