A switched virtual interface (SVI) is a virtual Layer 3 interface that can
be configured for any VLAN that exists on a Layer 3 switch. It is virtual in
that there is no physical interface for the VLAN and yet it can accept
configuration parameters applied to any Layer 3 router interface. The SVI for
the VLAN provides Layer 3 processing for packets from all switch ports
associated with that VLAN. Only one SVI can be associated with a VLAN. You
configure an SVI for a VLAN for these reasons:
- To provide a default gateway for a VLAN so traffic can be routed between
VLANs
- To provide fallback bridging if it is required for nonroutable
protocols
- To provide Layer 3 IP connectivity to the switch
By default, an SVI is created for the default VLAN (VLAN1) to permit
remote switch administration. You must explicitly configure additional SVIs.
SVIs are created the first time interface configuration mode is entered
for a particular VLAN SVI interface. The VLAN corresponds to the VLAN tag
associated with data frames on an ISL or 802.1Q encapsulated trunk or to the
VLAN ID configured for an access port. Configure and assign an IP address to
each VLAN SVI that is to route traffic off of and onto the local VLAN.
SVIs support routing protocol and bridging configurations.