Difference between VLAN

[cisco]

Hi,

whats the difference between layer 2 VLAN and Layer 3 VLAN.

regards

Neo

[gpulos]

a VLAN is a VLAN...no matter what layer they call it.

basically a VLAN is a layer-2 entity.

if you have what may be called a "layer 3 VLAN" then what you actually have is:

1) a layer 2 VLAN

2) a router (usually in the switch itself) configured with a VLAN interface to perform VLAN routing.

VLAN routing is required when you need a device in one VLAN to communicate with a device in another VLAN.

(remember, both VLANs in this case are still layer-2, they just also have a layer-3 interface/ipAddress to be used as routing interfaces)

[cisco]

Hi,

Thanks for your response , actually i am aware of this , but i thought that there might be some other defination for Second layer VLAN and third Layer VLAN.

regards

Neo

[sundar.palaniappan]

Here's the IEEE 802.1 defintion of VLAN. This is basically your layer 2 VLAN.

• Provides for the logical grouping of stations (MAC Service Access Points - MSAPs) and/or switch ports, allowing communications as if all stations/ports are on the same physical LAN segment. This includes stations/ports that are physically located on different LANs or segments within the physical boundary of an 802.1D Bridged LAN. A single Bridged LAN may include multiple VLAN “segments”.

With that said, as the previous poster mentioned, for a host on a VLAN to communicate with a host on another VLAN you need a layer 3 device (router). Often, this is done by a layer 3 switch (like 3550, 6500 etc.). On a layer 3 device you have to create a logical interface, vlan interface on a switch or sub-interface if you are doing router-on-a-stick, to route traffic between VLANs. This is basically your layer 3 VLAN (interface) if you like to call it that way.

HTH,

Sundar

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