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VLAN Interfaces
A VLAN interface or a switch virtual interface (SVI) is a virtual routed interface that connects a VLAN on
the device to the Layer 3 router engine on the same device. Only one VLAN interface can be associated with
a VLAN, but you need to configure a VLAN interface for a VLAN only when you want to route between
VLANs or to provide IP host connectivity to the device through a virtual routing and forwarding (VRF)
instance that is not the management VRF. When you enable VLAN interface creation, Cisco NX-OS creates
a VLAN interface for the default VLAN (VLAN 1) to permit remote switch administration.
You must enable the VLAN network interface feature before you can configure it. The system automatically
takes a checkpoint prior to disabling the feature, and you can roll back to this checkpoint. For information
about rollbacks and checkpoints, see the System Management Configuration Guide for your device.
You cannot delete the VLAN interface for VLAN 1.Note
You can route across VLAN interfaces to provide Layer 3 inter-VLAN routing by configuring a VLAN
interface for each VLAN that you want to route traffic to and assigning an IP address on the VLAN interface.
For more information on IP addresses and IP routing, see the Unicast Routing Configuration Guide for your
device.
The following figure shows two hosts connected to two VLANs on a device. You can configure VLAN
interfaces for each VLAN that allows Host 1 to communicate with Host 2 using IP routing between the VLANs.
VLAN 1 communicates at Layer 3 over VLAN interface 1and VLAN 10 communicates at Layer 3 over VLAN
interface 10.
Figure 3: Connecting Two VLANs with VLAN Interfaces
Loopback Interfaces
A loopback interface is a virtual interface with a single endpoint that is always up. Any packet that is transmitted
over a loopback interface is immediately received by this interface. Loopback interfaces emulate a physical
interface.
Cisco Nexus 5000 Series NX-OS Interfaces Configuration Guide, Release 5.2(1)N1(1)
78-26881-OL 35
Configuring Layer 3 Interfaces
VLAN Interfaces