Vishal
It is basically the difference between L2 and L3.
A vlan is a L2 concept. All devices with a vlan are in the same L2 broadcast domain. They are usually given an IP address frfrom the same subnet so one vlan = one subnet.
So if you created a vlan on your switch ie.
switch(config)# vlan 10
switch(config-vlan)# name v10
then you have created a L2 broadcast domain. All clients in this vlan can communicate with each other without any L3 routing needed. They communicate with each other by using each other's mac-addresses. You can view the L2 vlans on your switch by issuing the command "sh vlan brief".
If you create 5 vlans on your switch using the above commands and you do not create an SVI for each vlan then clients in each vlan will only be able to talk to clients in the same vlan.
If you you want the clients in one vlan to be able to communicate with clients in another vlan then you need to be able to route the traffic. To enable inter-vlan routing you would create a L3 SVI for each vlan you want to be able to route traffic for. So if you have 5 vlans, vlans 5 - 10 -
1) you create the vlan at L2 with the commands previously given
2) if you then create L3 SVIs for vlans 6 and 7 then -
clients in vlan 5 can only talk to clients in vlan 5. Same for vlans 8,9 & 10.
clients in vlans 6 & 7 can talk to clients within their own vlans and they can also talk between those 2 vlans. But note they cannot talk to any clients in vlans 5, 8 - 10.
Jon
