Information AboutVlan |
| CATEGORIES ABOUT VIRTUAL LAN | |
| local area networks | |
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A VLAN consists of a network of computers that behave as if connected to the same wire - even though they may actually physically connect to different segments of a LAN. Network administrators configure VLANs through software rather than hardware, which makes them extremely flexible. One of the biggest advantages of VLANs emerges when physically moving a computer to another location: it can stay on the same VLAN without the need for any hardware reconfiguration. PROTOCOLS AND DESIGN The IEEE 802.1Q tagging protocol dominates the VLAN world. Prior to the introduction of 802.1Q several proprietary protocols existed, such as Cisco 's ISL (Inter-Switch Link, a variant of IEEE 802.10 ) and 3Com VLT (Virtual LAN Trunk). Some users now deprecate ISL in favor of 802.1Q. Early network designers often configured VLANs with the aim of reducing the size of the Broadcast Domain in a large single Ethernet segment and thus of improving performance. When Ethernet Switch es made this a non-issue (because they have no collision domain), attention turned to reducing the size of the Collision Domain at the MAC layer. Virtual networks can also serve to restrict access to network resources without regard to physical topology of the network, although the strength of this method remains debatable as VLAN Hopping is a common means of bypassing such security measures. Virtual LANs operate at layer 2 (the Data Link Layer ) of the OSI Model . However, administrators often configure a VLAN to map directly to an IP network, or subnet, which gives the appearance of involving layer 3 (the Network Layer ). In the context of VLANs, the term "trunk" denotes a network link carrying multiple VLANs which are identified by labels (or "tags") inserted into their packets. Such trunks must run between "tagged ports" of VLAN-aware devices, so are often switch-to-switch or switch-to-). A Router (Layer 3 switch) serves as the Backbone for network traffic going across different VLANs. On Cisco devices, VTP (VLAN Trunking Protocol) allows for VLAN domains, which can aid in administrative tasks. VTP also allows "pruning", which involves directing specific VLAN traffic only to switches which have ports on the target VLAN. EXTERNAL LINKS
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