Free Cisco CCNA Training: Virtual LANs (VLANs)

VLANs, or virtual LANs, help us accomplish the important task of limiting broadcasts. Switches on any network are by default set on broadcast mode. For example with 80 switches, if one broadcasts all the 79 others receive it. They in turn might generate their own broadcasts in response to it and the process cascades hereon. This results in the cause of what is called a broadcast storm. Not only does it eat up the bandwidth, but it also is a huge waste of switch resources. This causes the switch to become practically useless for the network and reduces the overall speed of the network.

VLAN 1

Through VLANs, the scope of these broadcasts can be limited. They can be directed only to go to those destinations where they need to go. To do this, one needs to assign common VLANs to a particular number of switches which are concerned with each other’s broadcasts. IP addresses are assigned to all hosts. Pings can be sent around to test the network for connectivity. All CISCO switches are on VLAN 1 by default with ports 11 and 12 trunking. Cisco discovery protocol helps identify the devices directly connected to the device we run the command for.

A Router

Now hosts can be placed in common VLANs making them a sort of secluded group within the subnet. First it has to be made an access port so that it can’t trunk and is under one and only one VLAN. This is done by the switch port mode access command and specifying VLAN. Now, it is important to note that not only pings and broadcasts, but absolutely no traffic or data may travel between two VLANs, and devices in those VLANs without the use of a L3 device; here, a router.

Enhanced Security

VLANs have uses that exceed the limited scope of controlling broadcasts. They can be used to group network users by departments, authorization or any other relevant criteria for the network. This allows departments to have data that is exclusively visible only to the devices on their VLAN, thus making for greater security.

Ready to get Cisco certified? Learn how to install, operate and troubleshoot a small to medium enterprise branch network with our Cisco CCNA Training course.

More Related Posts

1. New Training Release: Cisco CCNP BSCI Training
2. New Training Release: Cisco CCNP BCMSN Training
3. New Training Release: Cisco CCNP ONT Training
4. New Training Release: Cisco CCENT Training
5. Jumpstart Your Career and Use Cool IT Toys: Get CCNA Training!