Technology: Network
Area: Networking General
Vendor: Cisco
Software: 12.X , 15.X
Platform: Catalyst switches, Nexus Switches

A Switched Virtual Interface (SVI) is routed interface in IOS representing the IP addressing space for particular VLAN connected to this interface. There is no physical interface for the VLAN and the SVI provides the Layer 3 processing for packets from all switch ports associated with the VLAN.

With SVIs the switch will use virtual Layer 3 interface to route traffic to other Layer 3 interface thus eliminating the need for a physical router. VLANs reduce the load on a network by dividing a LAN into smaller segments and keeping local traffic within a VLAN. However, because each VLAN has its own domain, a mechanism is needed for VLANs to pass data to other VLANs without passing the data through a router.

To configure the SVI, ensure your switch has a VLAN represented by the SVI you want to create:

Switch#vlan database
Switch(vlan)#vlan 2

Configuring the VLAN interfaces with the IP address:

Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#interface Vlan2
Switch(config-if)#ip address 10.1.4.1 255.255.255.0
Switch(config-if)#no shutdown