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A virtual local area network (VLAN) is any broadcast domain that is partitioned and isolated in a computer network at the data link layer (OSI layer 2). [ 2 ] [ 3 ] In this context, virtual refers to a physical object recreated and altered by additional logic, within the local area network .
This is known as inter-VLAN routing. On layer-3 switches it is accomplished by the creation of layer-3 interfaces (SVIs). Inter VLAN routing, in other words routing between VLANs, can be achieved using SVIs. [1] SVI or VLAN interface, is a virtual routed interface that connects a VLAN on the device to the Layer 3 router engine on the same device.
IEEE 802.1Q, often referred to as Dot1q, is the networking standard that supports virtual local area networking (VLANs) on an IEEE 802.3 Ethernet network. The standard defines a system of VLAN tagging for Ethernet frames and the accompanying procedures to be used by bridges and switches in handling such frames.
In case of Back-to-Back, VRF is necessary to create VLANs and subsequently sub-interfaces (VLAN headers and DLCI headers for Ethernet and Frame Relay network packets) on each interface used for the NNI circuit. In the case of eBGP NNI interconnection, IP routers are taught how to dynamically exchange VRF records without VLAN creation.
Cisco Inter-Switch Link (ISL) is a Cisco proprietary link layer protocol that maintains VLAN information in Ethernet frames as traffic flows between switches and routers, or switches and switches. [1] ISL is Cisco's VLAN encapsulation protocol and is supported only on some Cisco equipment over the Fast and Gigabit Ethernet links.
Conversely, an administrator can combine systems on separate local area networks (LANs) into a single VLAN spanning segments of a large network. External network virtualization is envisioned to be placed in the middle of the network stack and help integrating different architectures proposed for next generation networks.
Prior to supporting standardized IEEE 802.1Q tagging, 3Com used proprietary Virtual LAN Trunking (VLT). [5] 3Com VLT supported VLAN IDs 1–16 with 15 being reserved for Autoselect VLAN Mode (where a VLAN server decides port membership) and 16 reserved for Spanning Tree Protocol.
In computer networking, TUN and TAP are kernel virtual network devices. Being network devices supported entirely in software, they differ from ordinary network devices which are backed by physical network adapters. The Universal TUN/TAP Driver originated in 2000 as a merger of the corresponding drivers in Solaris, Linux and BSD. [1]