I have a switch on which all the network lights are going crazy on and none of the systems have network access or internet access. Below is my detailed configuration. I have 2 routers (DLink and Beetel) and one dlink 16 port switch.

The first DSL router that provides Internet access, has 4 ports. Port 1 and 2 are connected to 2 desktops. A straight cable goes from port 3 to 16 port dlink switch to provide internet access to 7 other computers.

There is a crossover cable going from the last port into another wireless router 18 feet away acting as access point for laptops.

The Dlink switch is an unmanaged switch, with no uplink port.

The network lights are blinking like crazy and no internet access or network access is taking place.

  • 3
    Poweroff the switches and then back on.
    – mailq
    Oct 20, 2011 at 10:39
  • 3
    "turn it off and on again" is step one in the 'how to fix anything IT related' guidebook. The second (and final) step is "bin it, buy new". Failure of step two leads back to step one. I have a flowchart here which helps greatly in problem resolution.
    – Sirex
    Oct 20, 2011 at 10:54
  • 1
    ... or if that somehow didnt work (almost unheard of), break out wireshark and see what traffic is flooding the network. You may have looped a cable on a switch without STP turned on.
    – Sirex
    Oct 20, 2011 at 10:56
  • 1
    I encountered these exact symptoms where someone had looped a cable into a hub, in this case powering off and on again will not help. You need to start removing cables until it stops. As @sirex says Spanning Tree can prevent this from causing complete meltdown in the future
    – Matt Wilko
    Oct 20, 2011 at 15:31
  • 1
    It sure sounds like a loop but the description of how things are connected doesn't bear that out, although their may be connections the OP isn't aware of.
    – joeqwerty
    Oct 20, 2011 at 20:56

3 Answers 3


Based on your description of how everything is connected it doesn't sound like you have a network loop, although the symptoms sound like it. My guess would be that you have some type of flooding going on in the network. Start by unplugging cables from the switch one at a time until the lights stop flashing like crazy. When they do find out what device is connected to that port and investigate it.

  • 2
    This answer is too simple. And too correct.
    – mailq
    Oct 20, 2011 at 11:49

Divide and Conquer

1) Disconnect the AP from the DLink switch. Are the lights still flashing like crazy 2) If yes Disconnect the Dlink switch from the DSL Router. Can the PC's attached directly to the DSL Router now connect to the internet. If they can't reboot the DSL Router then the two directly attached PC's and try again. If still no luck likey to be a DSL router Problem. If the problem goes away when the DLINK switch is removed then you need to start removing devices from this switch.

In addition did you disable DHCP on the second Router that was turned into an access point.


I think, you should switch off both of them. Then turn on first primary(where you have you direct link) and then secondry.

Assertion: It will configure the IP on router and will not go for loop or mesh!!

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