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Catalyst 2950s and isl trunking support

uwimona
Level 1
Level 1

why does the ios release with cat 2950 series switches not support isl trunking? I have checked the documentation and not see any reference to isl only dot1q trunking. In my environment we have multiple 2900,3500 and cat5k switches connected via isl trunks. Does anyone know why Cisco has left this out and is using dot1q as the only option?

7 Replies 7

millerv
Level 1
Level 1

Like the cat 4000, they are moving away from the proprietary to the standard.

ok so they are standardizing. Thought so. So I am stuck with dot1q.

Isn't isl more efficient than dot1q?

I don't think isl is more efficient. Just compare the header size.

david.hubbard
Level 1
Level 1

I don't know specifically about the 2950's, but I know that the cat4000's only support 802.1Q as well. We have been forced to use ISL and 802.1Q in our Enterprise as well. Don't know if that is a "bad" thing, it just makes management a little tougher sometimes.

You should upgrade your cat2900/3500 to IOS Enterpise Edition, This version can support ISL and dot1q trunk.

There is no Standard/Enterprise edition for Cat2950. The only IOS downloadable from CCO is "Enterprise" (see show version CLI command output).

mike.harlow
Level 1
Level 1

What can I do about my 100+ 1924's that I need to connect to my new 2950's? The 1924's only support ISL even with the latest firmware (9.00.04). This is the first I have heard of ISL support being dropped.

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