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VLANs can also help create multiple layer 3 networks on a single physical infrastructure. VLANs are data link layer (OSI layer 2) constructs, analogous to Internet Protocol (IP) subnets, which are network layer (OSI layer 3) constructs. In an environment employing VLANs, a one-to-one relationship often exists between VLANs and IP subnets ...
Private VLAN, also known as port isolation, is a technique in computer networking where a VLAN contains switch ports that are restricted such that they can only communicate with a given uplink. The restricted ports are called private ports .
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.
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.
For example, the sample diagram does not indicate the physical type of connection between the PCs and the switch, but since a modern LAN is depicted, Ethernet may be assumed. If the same style of line was used in a WAN (wide area network) diagram, however, it may indicate a different type of connection.
A VLAN access control list (VACL) provides access control for all packets that are bridged within a VLAN or that are routed into or out of a VLAN. Unlike regular Cisco IOS access control lists that are configured on router interfaces and applied on routed packets only, VACLs apply to all packets.
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.