Why use VLAN?

[wuitsung]

I know the basic of VLAN. It's a virtual lan in its broadcast domain created by switch. Normally it's the router creating the broadcast domain.

My question is why don't just use router?? so we don't have the hassle of configuring VLAN...

 

[unclerico]

Think about the size of the router that you would need if you had to segment your network into 10 LAN's for whatever reason. Making use of VLAN's allows you so much flexibility in how you configure your network. Just like with server and storage virtualization, VLAN's allow you to use your resources to the fullest.

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[lerdalt]

In a small site, I'd say you are correct...just use the router.

However, in a campus environment with multiple access layer closets, it becomes more efficient to use vlans to reduce your broadcast domains. Also a security component can come into play. Separating out certain networks from each other.

 

[VinceWhirlwind]

I think your question demonstrates you have commonsense:
In a basic sensible network design, the VLANs are all homed on the "core" (usually a Layer-3 switch), and each edge-switch only needs 1 VLAN configured on it.

Add converged VoIP into the design, however, and you will need to face the "hassle" of configuring multiple VLANs.

 

[jneiberger]

If you used the router and did not configure VLANs on your switches, you'd need one router interface and one switch for every subnet. If you use VLANs and a trunk connection, you only need one connection between your router and switch and you then subdivide your single physical switch into multiple mini switches.