The virtual local area network (VLAN) is a software concept that goes beyond a single traditional local area network (LAN) to a set of LAN segments being directed by particular configurations. Its arrangements are done fully in software as it is taken as a logical entity. For it being a software concept its identifiers and arrangements should be done properly for it to function effectively (Marschke and Reynolds, 236). The most effective identification and handling of VLAN are done by frame coloring. VLANs have currently replaced the traditional network designs to avoid the use of limited broadcast VLANs.
VLANS are mainly applicable also because of their capability of avoiding broadcast floods in larger networks from consuming resources or causing unnecessary service denials. The traditional network designs are made with several flaws, for ,instance relocations of personnel and departments can be very difficult tasks, especially in the cases where the original location maintains its network sub-sections. A VLAN saves the situation of the user when the network gets so large and is encountering much traffic (Yeung and Wong, 132). However, most of the people find themselves using VLAN because the network which they are operating with has been using it.
A VLAN is recommended when one has more than 200 devices in case LAN, incase of broadcast traffic on the LAN when group of users is in need of security or they want to be on the same broadcast domain if running the same applications. Most people have reported some benefits after using VLANs. Which includes, reduced administration expenses which are associated with moves, adds, and changes, enabled leveraging existing investments, having flexible and scalable divisions, and enjoying controlled broadcast activities.
There are different types of VLAN through which a switch can distinguish between VLANS. They VLANs VLAN membership by port, by MAC address, by protocol type, and by IP subnet Address (Minoli et al, 205). The VLAN membership by port makes it clear to the user to which VLAN each port belongs. For instance, if a switch has six ports, ports 1-3 may b defined with VLAN 1, and 4-6 with VLAN 2. This type is disadvantaged because if the user happens to move from one place to the other, switch port reconfiguration must be done.
Every workstation has a MAC address which is associated with VLAN in this type of membership by MAC. When a workstation relocates, the switch automatically discovers (Marschke and Reynolds, 475) membership by protocol type is whereby one may decide to link all IP traffic with VLAN1 and all IPX with VLAN 2. Finally, membership by IP subnet Address whereby membership is based on the layer 3 header. The switch reads the layer 3 address and gets linked to a VLAN.
Frame tagging is the criteria used to determine the logical grouping of nodes into a VLAN. The two known types of frame tagging are explicit and implicit methods. Implicit tagging is used to enable a packet to belong to a VLAN on basis of media access control address. Explicit tagging has added a field on the frame such that dividing the VLAN association. The effective performance of frame tagging is at layer 2 and it needs only a little processing or administrative overhead.
The ciscos proprietary frame tagging method enables high consistency in maintaining VLAN configuration across the whole network. Mainly it makes use of layer 2 trunk frames to manage the addition, deletion, and when one wants to rename. On the other hand, it synchronizes virtual local area networks information within a VTP domain and the chances of any need to configure the same VLAN information on each and every switch used (Lammle, 756). It as well minimizes the possibility of configuration problems which may arise when changes are being made. These problems are highly controlled as they may lead to security violations as VLANS can at times cross connect in cases where duplicate names are being used.
Through the use of Cisco’s proprietary frame tagging method there are some benefits which are enjoyed by the user. For instance, there is VLAN configuration consistency across the network, mapping method which allows a VLAN to be trunked over several media (Castelli, 205). Moreover, more accurate tracking and monitoring of VLANS is made possible, improved reporting of added VLANS across the network is experienced, and finally the benefit of plug and play modeling when one is adding new VLANS.
However, this tagging method is also associated with some disadvantages which are mostly related to the spanning tree protocol which is the bridging loop connecting throughout he network. All the switches are operated by sharing the instructions with each other, and the switch can take part in only one domain. Switches which are found in different domain do not by any chance share VTP information.
In conclusion, the emergence and usage of virtual local area network has come to solve the limitations which were encountered by the use of the traditional network connections.
References
Castelli, Mathew. LAN switching first-step. Cisco Press, 2004.
Lammle, Todd. CCNA: Cisco Certified Network Associate Study Guide: Exam 640-802, John Wiley and Sons, 2007.
Marschke Doug and Reynolds Harry. JUNOS Enterprise Switching. O’Reilly Media, Inc., 2009.
Minoli, Emma. et al. Ethernet-based metro area networks: planning and designing the provider network. McGraw-Hill Professional, 2002.
Yeung Alan and Wong Angus. Network Infrastructure Security. Springer, 2009.