What is Vlans

[ITlover]

What is Vlans

I have heard that Vlans is used as a bridge between two networks but what is actually Vlans? I mean to say that what is its function?


Regards,

[mikezel]

http://webopedia.com/TERM/V/VLAN.html

hope that helps

mike

[DragonNOA1]

Look at a common household switch. You can only give it one IP and one subnet mask, making a LAN. Many business switches can change each port to a different IP and subnet, thereby making a VLAN (virtual LAN).
Home: 1 switch, 1 LAN
Business: 1 switch, many diferent LANs aka VLANs

[mbossman2]

VLANs allow the network admin to group various users (whether they are in the same area is immaterial) on the same network (subnet mask). This allows for superior security as wellas more efficient use of bandwidth.

From a scurity standpoint: imagine a company with 3 departments: sales, accounting and payroll. The sales folks have no need to view the information in accounting or payroll, accounting needs to see certain assets in sales (orders and the like) and some things in payroll (communicating when an order ifs filled so that commissions can be paid) and payroll needs nothing from sales but needs to hook up to accounting. So to segment the data you place sales in VLAN #1, Accounting in VLAN #2 and payroll in VLAN #3. with your standard layer 2 switch none of the other VLANs can "see" the others, so they (virtually) may as well not even exist (security).

But how, you ask, does payroll, accounting and sales share data? This is where a layer 3 switch comes into play. An L3 switch acts as a router as well as a switch and allows users to jump from 1 VLAN to another. Because an L3 switch can act as a router, you also have thee ability to build what are called access control lists (ACL's). These are a series of permissions that allow specific users to access specific networks and specific assets (servers, printers etc) on those networks. So in the above example, you could specify that Accounting can access the sales VLAN but only the server that contains the orders, but not the server that has the contact mangement software. So you can clearly define and specify network usage.

From the bandwidth perspective, you can assign certain high bandwidth applications (or devices) to a specific VLAN so that their bandwidth utilization does not affect other users. For example, in an IP telephony configuration, you would assign traditional data and computer usage to to VLAN A and voice traffic to VLAN B. As voice traffic is highly bandwidth intensive, it can affect data bandwidth and vice versa.

make sense?

[ITlover]

Thanks for providing such a useful information, I want to know what is the difference between routers and vlans?

Bye

[DragonNOA1]

Routers are physical/hardware, VLANS are software. Routers "can" contain VLANS, and VLANS are made up of one or more routers.

[mbossman2]

VLANs are a logical grouping of users: Users A, B and C are grouped together in VLAN (IP subnet) 1, Users D, E & F are grouped together in VLAN (IP subnet #2). In a "normal" flat (layer 2 only) network, VLAN #1 is invisible to/from VLAN #2. To allow traffic to flow from 1 discrete IP Subnet (in this case VLAN #1) to another discrete IP subnet (VLAN #2) you need a device that can direct traffic from one network to another and that is a router.

A router allows for data to from from 1 network to other networks.