Unstable LAN connection after replacing 100Mbps switches by 1Gbps switches


We have basically the following setup:
router -> switch 1 -> switch 2

We have Cat5 cables between the router and switches. We decided to replace the really old 100Mbps switches by 2 new (1Gbps) Netgear ProSafe GS108GE switches. We also replaced the cables between the end user devices and the switches from Cat5 to Cat6.

The problem is, that the connection between switch 1 and switch 2 is unstable. I had trouble getting the switches to recognize that the cable is active in the first place. It then worked for an evening. This morning I had to move one of the switches (remove the power source) and again what followed was 10min of restarting either switch and moving the cable to another free port to get it to build the connection. Currently the connection stays stable for 3min up to what is now ~1h (still ongoing) until the LEDs on the switches extinguish for that specific port and the end user devices show that there's no connection anymore.
Replacing switch 2 directly by a laptop (with Gigabit Lan) still led to problems.

The Cat5 cable is displayed to have a 1Gbps connection running and the performance during the time it works is with data rates of 20MB above the 100Mbps. During the evening which it worked without problems I think to remember that it was displayed to have a 100Mbps connection and the performance was accordingly.

I unfortunately can't replace the Cat5 cable between switch 1 and switch 2 but could recramping that cable help? Or do you have any other suggestions / ideas what the problem could be?

I'll gladly provide any additional information I can that you deem helpful.

Thanks for any help!

3 answers Last reply Best Answer
More about unstable lan connection replacing 100mbps switches 1gbps switches
  1. Get a cable tester like this:
    and test the cables. In fact Cat5 or Cat6 doesn't really matter, but you need all eight lanes (4 twisted pairs) working for 1GB instead of four for 100Mbit. Recramping might help.
  2. Is it cat5 or cat5e?

    How long is cable connecting switch?
  3. Best answer
    It is very common to get results like yours when the ends are not on correctly. Of course you could have the pair wrong so reverify that both ends follow the standard color pattern for 568a or 568b. Either is fine just make sure both are the same.

    This is part of the reason I recommend people who have not made a lot of cable to buy premade ones if possible. It is a matter of practice. Generally the problem is that the wires do not fully seat to the end of the plug this means you are getting a connection but it is not good enough to pass data. This unfortunately will pass the cheap led cable testers since those only validate you have the pairs correct. You would need high end tester that even many professional cable guys have trouble affording.

    This is one of those things after you have made 100s of cables you can just feel when the cable slides to the end on all 8 wires correctly. Take a bright light and verify that all 8 wires go in as far as they can.

    More than likely you could just cut off both end reterminate them and you will get lucky the second time.

    It may also be worth getting a commercial made cable that you can lay over the floor just to verify that it is the cable before you go to a lot of trouble.
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