From: Howard C. Berkowitz (hcb@gettcomm.com)
Date: Mon May 30 2005 - 13:30:32 GMT-3
At 11:17 AM -0500 5/30/05, Bajo wrote:
>Hi Quetta,
>
>Pls. check http://www.cisco.com/warp/public/473/741_4.html
>
>ISL is a Cisco proprietary protocol for interconnecting multiple
>switches and maintaining VLAN information as traffic goes between
>switches. ISL provides VLAN trunking capabilities while maintaining
>full wire speed performance on Ethernet links in full-duplex or
>half-duplex mode. ISL operates in a point-to-point environment and
>will support up to 1000 VLANs.
>
>
>802.1Q is the IEEE standard for tagging frames on a trunk and supports
>upto 4096 VLANs.
>
>
>On 5/29/05, Quetta Walla <quetta_1@lycos.com> wrote:
>> Hey,
>>
> > What are differences between ISL and 801.1q other than the 802.1q
>header size is smaller. Whats the total number of vlans supported in
>802.1q and what is it in ISL?
>>
This may be TMI (too much information), but they represent different
design approaches. ISL is really a tunneling protocol, which puts a
L2 header in front of the existing one. 802.1q inserts a field into
the standard header.
One advantage of ISL, which has been largely overtaken by events, is
that it handled frame types transparently. Ethernet II, 802.3 with
and without 802.2, Token Ring, etc. all could be carried.
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