Is there a guideline published that considers the total number of 100 MB ethernet ports on a switch and then recommends an appropriate size for the gigabit ethernet channel (trunk) connecting the switch to the rest of the network ?
Not sure that a chart actually exists, but the answer is probably determined by several factors. What is the function of the trunk? Is it an uplink from an access layer switch or a connection between two core devices? Does the access layer switch have Servers connected to it, or general use desktop computers? How is your network used (lots of voice/video, large file transfer traffic)?
Oh and btw, in a wiring closet with desktop computers, you shouldn't be concerned with 15:1 or even 20:1, and that number seems to grow as more and more gigabit desktops are being sold. Just because that machine has a gigabit nic, doesn't mean it could actually perform at a level that would actually utilize 1 Gbps.
I think it would be interesting to consider all the scenerios, but let's just say generically it's a fully loaded 4500 series switch in a wiring closet and you're trunking it back to a core switch in the data center. The traffic is office printing, shared drive access on several W2K servers, and outlook e-mail primarily. I have yet to see a Cisco press book that explains how to do the actual engineering on different scenarios -- they are great for telling you the concepts and the configuration commands to make it happen -- but what about the math ? What should the assumptions be ? At least 1 megabit per second guaranteed under peak conditions ? More ?
Kev> Not sure that a chart actually exists, but the answer is probably
Here is a Cisco link pitching 10gig uplinks and it has some discussion of oversubscription from the closets. Of course they want you to buy the 10gig solution.
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