Reference Guide

372 | Interfaces
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FTOS supports Inter-VLAN routing (Layer 3 routing in VLANs). You can add IP addresses to VLANs and
use them in routing protocols in the same manner that physical interfaces are used. For more information
on configuring different routing protocols, refer to the chapters on the specific protocol.
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:
Figure 20-8 shows a sample configuration of a VLAN participating in an OSPF process.
Figure 20-8. Sample Layer 3 Configuration of a VLAN
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:
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.
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
!