Cat 7 cables with Cisco 3750 and Cisco IP Phones

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May 22nd, 2007
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We are building a new office and going to choose Cat7 wiring.

I'm wondering if there any specific requirements or issues for using this with our Cisco 3750 switches, Cisco 2600 router, and Cisco 7940/7960 IP Phones. Thanks,


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bjw@gty.ci.hend... Tue, 05/22/2007 - 12:57
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The only issue I see besides being very expensive, is the overall thickness of Cat 7/Class F cabling. It may be difficult to patch fill 24/48 ports on a 3750, Cat 7 is thick and not as easy to bend as older cabling.


You'll need to plan a larger backbone conduit/tray system. Whereas 1" SAE conduit can comfortably take 7-8 Cat 6 cables, but only 3-4 Cat 7. There could be some financial impact to the cost feasibility of Cat 7.


If you are planning for 10G+ to the desktop in the next 10+ years, or your office area is subject to heavy electrical/radio interference (Manufacturing Plant/RF Room), then Cat 7 is probably worth the money, but for the cost you incur, it might be wiser to look at a cost benefit analysis of 50um MMF to the desktop, I bet it's orders of magnitude cheaper and less susceptible to conduit size issues and interference.


Also, Cat 6 can carry 10GB up to about 50m, cat 6E to 100m, I would certainly look at that as well.


Any way that's my 2 pennies.


Bill


jasonrandolph Tue, 05/22/2007 - 15:26
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Cat 6a is in the process of being rated to 10Gb/s for a 90 meter (horizontal) run. Cat 7 technically doesn't work for 8P8C (RJ45) due to the size of the cabling.


MMF by itself gets rather expensive in a hurry. The switchport cost is also prohibitive. The difference list price cost between a WS-X6748-SFP (48 port SFP) blade for a 6500 series and a WS-X67-48-GE-TX (48 port 10/100/1000 blade) is $10,000. They share the same subscription ratio.


This doesn't include the $500 per port list price cost of the SFP modules for the 48 port switch blade which means you're shelling out an additional $24,000 (again list) for the same throughput.


Obviously this makes assumptions based on hardware, I do not believe there is a current 48 port LC standalone gigabit switch. The existing 48 port blades for 4500 and 6500 series switches require SFPs.


For that cost you could very likely re-cable the office again in the future if you need to.

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