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I have a D-Link 8-port Ethernet switch which was perfectly working. Since 2 days ago it makes the entire network down. The problem is when I disconnect the cables it runs again and after I connect "the last cable" it goes down again. No matter which cable is the last one, it becomes unstable and the network goes down. I've checked for IP conflicts and many other things, but I didn't find any clues to my problem. I even replaced the switch with a new one, but still there is no hope. Please help me find the problem.

HopelessN00b
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M Ramezani
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    http://en.wikipedia.org/wiki/Switching_loop – Chopper3 Aug 04 '14 at 09:47
  • @Chopper3: Thanks, but it used to work for more than 5 months and there is no change in the network topology. – M Ramezani Aug 04 '14 at 09:57
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    @MRamezani The problem description matches the behavior to be expected from a switching loop. Most likely either you don't remember all the details about your network topology, or somebody made a change to your network topology, which you are not yet aware of. – kasperd Aug 04 '14 at 12:08
  • What do each of the cables you are connecting to the switch go to? Be as precise as possible. – David Schwartz Aug 04 '14 at 12:16
  • Max, your network topology has definitely changed. Where there any changes made to your server, i.e. a bridge setup? – user2092982 Aug 04 '14 at 11:32
  • No, I'm sure that nothing has changed. – M Ramezani Aug 04 '14 at 11:43
  • One is Uplink (Connects to another switch), the rest are connected to the workstations. – M Ramezani Aug 04 '14 at 15:18
  • So from what I read in your comment you've got a network setup with a server, two switches and a bunch of workstations. What's the second switch for? Did I get you right that the troublemaker switch is not directly connected to the network circle but through another switch? Why is this? Please provide more detail on the topology. I'm pretty sure it is a switching loop problem. – user2092982 Aug 04 '14 at 21:13
  • @MRamezani Confirm that none of the workstations have more than one Ethernet connection. Perhaps some fool has tried to put a computer on "both networks" and formed a loop in the process. – David Schwartz Aug 04 '14 at 22:45
  • None of the workstations has more than one NICs. I tried disconnecting one of the connection which was a network printer (HP 400dn). Seems like the problem gone, but I have to check it tomorrow to see if it really solved or not... – M Ramezani Aug 05 '14 at 15:22
  • @user2092982 I am sure that there isn't a loop here. Yeah, the troublemaker switch is not directly connected to the network circle and it is because somehow in the middle we have some workstations... – M Ramezani Aug 05 '14 at 15:24

1 Answers1

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Swap it out for a different working switch. If it is still broken then your network topology HAS changed.

JamesRyan
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