As you know, 802.1q is a standard while ISL is proprietary. If you need
interoperability, go with 802.1q. Even if you're all Cisco, some of
Cisco's stuff doesn't support ISL. I say use whatever is available and
works for you, keeping in mind that reconfiguration in the future will
be necessary if you change trunk types. If that's not a big deal, I
wouldn't worry about it. If it will cause a horrendous headache to have
those trunks down for a minute or two while you reconfigure, then think
toward the future and pick 802.1q. <g>
I have noticed a configuration difference between the two. It was
supposedly fixed in IOS 12.1(2), I think, but I've noticed this in
12.1(5) still. When using ISL, all of your VLANs are placed on
subinterfaces on the router. This is because all frames coming across
that trunk have an ISL tag for VLAN determination.
In 802.1q, the native VLAN (VLAN 1 by default) is not tagged so you
have to place the configuration for that VLAN on the major interface.
All other VLANs would be on subinterfaces.
Regards,
John
>>> "Lopez, Robert" <[EMAIL PROTECTED]> 3/23/01 7:57:24 AM >>>
What are the differences between isl and 802.1q trunking. If I'm in a
total
cisco switched environment, should I always use isl? What would be a
good
reason to use 802.1q? Which one is more favored over the other?
Robert
Robert M. Lopez
Network Planning
Ann Arbor Data Center
Pfizer Global Research & Development
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