what is disadvantage of IEEE 802.1Q over ISL?

devang_etcom · ‎09-25-2005

what is disadvantages of dot1Q ...?

cisco switches support both ISL and dot1Q but is there any special case where we can prove ISL is superior than dot1Q??????????

ankurbhasin · ‎09-25-2005

Hi Devang,

There is no advantage of isl over dot1q. Infact ISL increase the size of the frame by 30 bytes which includes 26 byte of header and 4 byte of tailer.

Dot1q just uses 4 bytes of internal tagging which does not affect the size of the frame much.

Also dot1q is open standard so can be used between multivendor switches.

HTH

Ankur

glen.grant · ‎09-25-2005

Also ISL is cisco proprietary and you cannot use ISL to connect to other vendors equipment whereas dot1q is the standard.