Frame Tagging(802.1q) over Frame Encapsulation(ISL).

viper75

I have 2 simple questions:

1) Why did Cisco produce the 2950 switches to support 802.1q instead of ISL??? To me it makes no sence. Every other switch that Cisco makes all support ISL. Go figure .

2) What is there a true advantage of having one over there other???
From my understanding and from reading and working with ISL\802.1q, 802.1q modifies the frame while ISL ecapsulates the frame.

sanjana

ISL is cisco proprietery and 802.1q is compatible with other vendor devices, which is the obvious advantage.

dswillieus

Also, 802.1Q tagging uses less overhead to your network trunks, where ISL adds a new header and trailer around the entire frame, 802.1Q only inserts 4 bytes into the IP Header.

viper75

Thanks fellas!!!

That's what I thought, but I wasn't sure if there was something else I was missing.

I think it's pretty dumb of Cisco to make some switches (most) ISL capable and some 802.1q.