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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.

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closed as off-topic by HopelessN00b, mdpc, MichelZ, Jed Daniels, Falcon Momot Aug 14 '14 at 20:33

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@Chopper3: Thanks, but it used to work for more than 5 months and there is no change in the network topology. – M Ramezani Aug 4 '14 at 9:57
Max, your network topology has definitely changed. Where there any changes made to your server, i.e. a bridge setup? – user2092982 Aug 4 '14 at 11:32
No, I'm sure that nothing has changed. – M Ramezani Aug 4 '14 at 11:43
@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 4 '14 at 12:08

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

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I did it before...No hope! I'm looking for a change, but nothing is found yet! – M Ramezani Aug 4 '14 at 10:58

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