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Not sure if this is the right place to ask this question. But I have a router which connects to the internet. Now I have a switch connected to this router. I added a lot more computers so I added another switch and connected it to the first switch using a cross-over cable.

As soon as I connect it to the first switch, my lights in first switch start blinking like crazy and my entire network simply stops working. The minute I remove the second switch's wire, its all fine again.

What could be the problem?

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What kind of router and switches? – squillman Aug 11 '09 at 4:40
all 3 are d-link. new one is a 16 port dlink. the first switch is a 8 port dlink. router is also dir-300. – elated Aug 11 '09 at 4:43
also my first switch (8port) is rather old. could that be the reason why it starts blinking like insane and is not able to handle the load? – elated Aug 11 '09 at 4:45
up vote 8 down vote accepted

This sound suspiciously like you have the switches plugged into eachother in a circle. E.g. Switch A is plugged into Switch B which is plugged into Switch C which is plugged into Switch A. So broadcasts go A -> B -> C -> A -> B -> C -> A -> B -> C so on and so on at the maximum speed the switch will support, thus rendering the network unusable.

Make sure that none of the switches are plugged into any other switches except for that central switch (the router. Which I'm guessing is a consumer grade router that also has a switch in it).

Edit: Just saw your comments about the brands of the products. For clarifications sake, you actually have three switches in your scenario (your DIR-300 has a router AND a switch. It's the switch that's causing the issue here).

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it was indeed a loopback. fixed that and bought a new 8port router cause mine randomly died. all working now :) – elated Aug 17 '09 at 16:56

Usually when I connect switches, I just use a regular cable because most of them switch automatically, although they should understand a crossover as well.

A few possible trouble shooting possiblities, if you haven't already tried:

  • remove everything from both switches and plug them in together
  • remove everything from the second swtich and plug them in together
  • put the second switch as the first one
  • add another switch and plug both switches into that switch
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If you're using a crossover cable make sure you're not plugging it into an uplink port on the switches.

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even if i use a regular cable, my network stops working. what is an uplink port, i thought all the ports on my switch were the same. – elated Aug 11 '09 at 4:56
An uplink port is a special port designed for connecting switches to other switches, and should only be used with a normal cable. If you don't know what it is, chances are your switch/router don't have them. – Mark Henderson Aug 11 '09 at 5:06

Connect modem to router via uplink port then run a crossover cable from 4 port switch in router to switch1/portX, then run a crossover cable from switch1/portY to switch2/portX then plug in devices as needed.

I would suggest that you use the older switch for the lest amount of traffic and/or as the switch2 in this example.

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