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Mixing ISL and 802.1q trunks

I currently have a 5509 backbone with MLS, using a trunk to a 7206 router to initiate routing between VLANS. I also have several other trunks to CAT 5000 and 2900 switches. ALL TRUNKS USE ISL.

Now I'm getting in CAT 4006s with SUP 2s and they only do 802.1q trunking. The technical sales contact says no problem. I can configure a trunk between the 5509 and CAT 4000 using 802.1q but my VTP domain info and VLANS don't show up. TAC support didn't find an answer.

Can I mix trunks or do I need to upgrade to SUP 3s on the 4000s and use ISL?

Is Cisco phasing out ISL? What's best for the future when I have 6500 backbone and 4000s in the closet? I will never have the need for implementing trunks with other vendor swtiches.

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Cisco Employee

Re: Mixing ISL and 802.1q trunks

You can have ISL and dot1q trunks terminating on the same switch and you should not have any issues with it. ISL is not being phased out but it's just that some hardware does not support ISL and moreover dot1q is an IEEE standard

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