Virtual Local Area Network -Introduction to VLANS

Introduction to VLAN

Virtual LAN is like a physical LAN in all respects except for it requires the end stations to form a group irrespective of them being attached to the same broadcast domain. The network setup of deploying the VLAN is simple. This is because a network can be configured or reconfigured in some cases using software only. The virtual LANs functions at the layer 2 of the OSI model that is the Data Link Layer

 Why VLANs are used?

The VLANs are built with a view to proffer segmentation, which is provided by routers in the wired physical LANs. VLANs can divide the network so that some of the hosts may make use of different Dynamic Host Configuration Protocol. VLANs are proficient enough to address the different network issues like security, network management and scalability. By deploying VLANs the traffic patterns are easy to mange and one can act in response to relocations. VLANs are also used when layer 3 multiple networks are created using the same layer 2 switches. Hence any dynamic host configuration protocol server can monitor any host on the network that wants to get its IP address from the DHCP server. This process or facility makes the network design simple. The major advantage of using VLAN is its simple and adaptive infrastructure.

The Types of Virtual LANs

Static and Dynamic VLAN are the two popular types of virtual local area networks. The static VLANs are also called port centered VLANs. Multiple ports are assigned to the VLANS in order to establish a static VLAN arrangement. When a static VLAN is established and a device comes into the network, it is automatically adjusted to the existing port settings. In other words we can say that the port is assigned to an entire virtual network and not the specific computer terminal. This shows that each independent user has become a member of the VLAN. On the contrary if any independent user wants to change the port assignment for new connection. The network has to be manually reconfigured for the desired changes. On the other hand the dynamic VLANs are created using plenty of softwares available in the market but most often they are built using Cisco works 2000. In this dynamic arrangement the network administered allocates the port based on the MAC addresses of the attached devices. Also a user name is assigned to the users for their secure operations. Hence whenever a new device is entered into the network it asks for the database settings in order to become the part of Dynamic VLAN.

The Working and the Working Standards for VLANs

IEEE 802.1Q is the guiding standard for the virtual LANs today. This standard provides VLAN with enough and vibrant vendor support. Early some proprietary standards like Cisco’s Inter Switch Link and 3Com’s virtual line trunk also remain attached to the working of VLAN. The ISL and IEEE standards perform their operations differently. In an IEEE 802.1Q standard works by making use of internal frame tagging, hence the data frames are tagged with virtual LAN information and Ethernet frames are modified. The working of the ISL is totally reverse, it works by performing external tagging to the frames and hence the frames are not modified. The working of the VLANs is often enhanced by mapping VLANs directly to the IP network. These multiple VLANs are identified by the tags inserted into their packets. The working of this trunk also takes place in the Tagged ports and devices which recognize the labeled data packets. Hence the network connections are often undeviating switch to switch or router to switch besides being a direct host to destination link.

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