Switch virtual interface
A switched virtual interface (SVI) is a VLAN of switch ports represented by one interface to a routing or bridging system. 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.
There is one-to-one mapping between a VLAN and SVI, thus only a single SVI can be mapped to a VLAN. By default, an SVI is created for the default VLAN (VLAN1) to permit remote switch administration. An SVI cannot be activated unless associated with a physical port.
SVIs are generally configured for a VLAN for the following reasons:
- Allow traffic to be routed between VLANs by providing a default gateway for the VLAN.
- Provide fallback bridging (if required for non-routable protocols).
- Provide Layer 3 IP connectivity to the switch.
- Support bridging configurations and routing protocol.
SVIs advantages include:
- Much faster than router-on-a-stick, because everything is hardware-switched and routed.
- No need for external links from the switch to the router for routing.
- Not limited to one link. Layer 2 EtherChannels can be used between the switches to get more bandwidth.
- Latency is much lower, because it does not need to leave the switch
An SVI can also be known as a Routed VLAN Interface (RVI) by some vendors.
- Cisco Systems, 2006, "Building Cisco Multilayer Switched Networks" (Version 3.0), Cisco Systems Inc.
- "Understanding Routed VLAN Interfaces on EX Series Switches". Retrieved 29 May 2013.
- Data Centre Networking Module (COMH9003) | Cork Institute of Technology
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