ISL and dot1q

[vishalpatil86]

hi,

in which scenarios we use ISL or dot1q?

thanks,

vish

[Jon Marshall]

When you want to create a trunk connection between devices, usually switches but it can also be routers, servers etc.

A trunk is link that carries multiple vlans and you therefore need to tag the traffic so the receiving device knows which vlan that traffic is meant to be in.

Jon

[vishalpatil86]

hi jon,

let me rephrase the question.

What's the difference between ISL and dot1q?

And how do you decide to use between these two?

[Jon Marshall]

Vish

See this thread for details as I think it covers all you are asking -

https://supportforums.cisco.com/discussion/12040596/isl-vs-dot1q

and if you still have questions after reading it then please feel free to ask further.

Jon

[Leo Laohoo]

And how do you decide to use between these two?

Not all switches support ISL.

ISL was, more or less, a proof-of-concept developed by Cisco and later ratified by IEEE to become Dot1Q.