Reference Guide

Interfaces | 421
A consideration for including VLANs in routing protocols is that the no shutdown command must be
configured. (For routing traffic to flow, the VLAN must be enabled.)
Assign an IP address to an interface with the following command the INTERFACE mode:
The following example shows a sample configuration of a VLAN participating in an OSPF process.
interface Vlan 10
ip address 1.1.1.2/24
tagged GigabitEthernet 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. Since 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 a Loopback interface, use the following command in the CONFIGURATION mode:
To view Loopback interface configurations, use the
show interface loopback number command in the EXEC
mode.
Note: An IP address cannot be assigned to the Default VLAN, which, by default, is VLAN 1. To assign
another VLAN ID to the Default VLAN, use the default vlan-id vlan-id command.
Command Syntax Command Mode Purpose
ip address ip-address mask [secondary] INTERFACE Configure an IP address and mask on the interface.
•
ip-address mask: enter an address in
dotted-decimal format (A.B.C.D) and 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.
Command Syntax Command Mode Purpose
interface loopback number CONFIGURATION Enter a number as the loopback interface.
Range: 0 to 16383.