Solved: linking three 2950s together

dreihs · ‎02-10-2004

Newbie question:

I am thinking of getting three 2950T-48 switches to replace some hubs. I only have one run from the closet to the server room so figured i would have to daisy chain them and just connect one back to the server room. These switches each have 2 10/100/1000 base-T ports. How are these switches linked and will I need crossovers for these connections?

Thanks for your help and patience.

konigl · ‎02-11-2004

I usually order them, or make them myself. When I have seen crossover cables in stores, 9 times out of 10 they are only 2 crossed pairs, good for 10/100 only.

Interesting, though, is that I have seen some switches (3Com) that have internal circuitry to auto-cross the copper ports when necessary. So you can use regular straight-through patch cables to link switches, and they take care of the crossing automatically.

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konigl · ‎02-10-2004

You are correct, your best option for three 2950T-48 switches in one closet is to daisy-chain the 10/100/1000 ports.

Let's say, 10/100/1000 port #1 into the 10/100/1000 port #2 of the switch above it, etc. until you get to the top switch in the stack, then connect that one's 10/100/1000 port #1 to the cable run to the server room.

You will need crossover cables for this, but not your average run-of-the-mill 10/100 Ethernet crossover, which crosses only two of the four pairs in a Cat5 or better cable. You need all four pairs crossed, according to the pinout in the following link:

Four Twisted-Pair Cable Pinouts for 1000BASE-T Ports

http://www.cisco.com/en/US/products/hw/switches/ps628/products_installation_guide_chapter09186a00800d7683.html#1019506

Hope this helps.

dreihs · ‎02-11-2004

Thanks for the input.

Question: are these 4 crossed pair cables available at your local PC Big Box store or do you find that they are regularly ordered?

Have a good day.

konigl · ‎02-11-2004

I usually order them, or make them myself. When I have seen crossover cables in stores, 9 times out of 10 they are only 2 crossed pairs, good for 10/100 only.

Interesting, though, is that I have seen some switches (3Com) that have internal circuitry to auto-cross the copper ports when necessary. So you can use regular straight-through patch cables to link switches, and they take care of the crossing automatically.