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VLAN and subnet diference

Hi dear experts!

In one internet site I found the definitions:

Subnet
This is a term that refers to a group of TCP/IP addresses. Addresses in the same subnet are reachable without going through a router, and thus can be reached by broadcast. To reach addresses outside of a particular subnet, you must transmit through a router. This is all part of the TCP/IP protocol.

VLAN
(Virtual LAN) A VLAN is created when a bunch of physically connected ports are grouped together by network hardware and software that supports VLANs. These VLANs are each treated as completely separate entities and can only be joined together by a router. This scheme is useful for grouping departments together for security and minimizing network traffic.

What is the main operative difference between a VLAN and subnet? logical, physical? I think they have the same purpose. Could we have various subnets in a VLAN? What is the optimum? One VLAN per subnet? I know that VLAN refers layer 2 business and subnet is layer 3 business. Both can be communicated by a router. Can somebody give me some comparisons?

Thanks in advance!
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arexturicum
Asked:
arexturicum
2 Solutions
 
gjohnson99Commented:
I think you got it

Think of each vlan a seperate netwok. (a vlan acts like normal Lan)

vlan 1 with subnet 192.168.1.x  

vlan 2 with subnet 193.168.2.x

You need a bridge or router to connect to two together(A layer 3 device).


But what's cool is

both vlans can run over same hardware (switchs and many lan card  now support Vlan)

If you have a level 2 Swtich only first packet go though the router the rest routed point point on the switch

Thiscan  be big speed boot to a network.

You can many subnet on vlan but would keep at 1 to 1.


Let me know if  need more info

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muhalokCommented:
Well you got that right about the layers: VLAN - layer2 , Subnet - IP layer, Layer 3.

Here is a link to a very good VLAN definition - very accurate and visual:

http://net21.ucdavis.edu/newvlan.htm#what

VLANs are basically used to connect several LANS into 1 broadcast domain. They don't add latency like routers , that connect Subnets.


VLANs operate in the same subnet, i.e. VLANs are connected by a Layer 2 switch (regular switch that supports VLANs). It is useful in case you have a range of IPs, i.e. a SUBNET which you want to divide into several segments without putting a router in between. So all machines will have the same default gateway for example or will be configured to work with the same DHCP server. But you will be able to separate traffic between the machines on the same subnet.
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