1) Cisco ISL is much better than urgly 802.1q - first of all, it was designed many years before 802.1q. I am not even talking abiout those idiots, who designed 802.1q as a _spanning tree on the trunk level_, which made many configurations (which we used with ISL ain 199x years) impossble, and caused vendors to extend 802.1q.
Is it April 1st? ISL changes the size of packets, does it not? So know you have to deal with MTU issues. What happens when I want the biggest MTU possible? I know it is not much a difference in size, but for some people, size does matter.
I am quite happy with dot1q. My gripe is with poor spanning-tree implementations. I don't want a single spanning-tree for every vlan on a trunk... I like standards, but I am happy with Rapid-PVST. Just my feelings about the issue. I would never deploy ISL unless I had something like a 1900 that did not do dot1q
Amen. At my previous employer, we got rid of ISL on almost all trunks. I wouldn't dream of going back. The only thing I don't really like about 802.1q compared to ISL is the idea of "native" or "default" VLAN. I want links to be either access (untagged) or trunk (*all* packets tagged). Fortunately, reasonably new Cisco switches let me enforce that with "vlan dot1q tag native". Steinar Haug, Nethelp consulting, sthaug@nethelp.no