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Community Member

disconnection from network

i have some new computer with intel network card Intel(R) 82566DC Gigabit Network and some time i get this message

Intel(R) 82566DC Gigabit Network Connection :Spanning Tree Protocol has been detected on the device your network connection is attached to.

and they disconnect and connnet from the lan i have cisco 3500xl stp is enable


Re: disconnection from network

Any changez has been made recently on the network(physically or made any changez in the config), because that might occur loop on the network.

Community Member

Re: disconnection from network


I Have also a BIG Problem with HP SFF PC's with Intel 82566 Gigabit Network Cards (OnBoard) with the same message.

My Problem is also a DISCONNECT (Layer1 LINK DOWN) and followed by a CONNECT (Link UP) after 1 Second.

My Switches are all 3500XL - With 3550 No Problem.

Configured PORTFAST and AUTO Negotiation

Fix Speed SET - No Change


Sometimes it helps when i change the Port or Patch to another Switch in the same Cabinet.

Please HELP - About 800 PC's (with about 20 with this Problem)


Community Member

Re: disconnection from network

We're running into very simliar problems.

You have Portfast disabled on ports connecting to switches or routers right?

are there updated drivers for the nics?

Community Member

Re: disconnection from network

I have portfast enabled.

But it doesn't make sense if i disable it.

NIC Driver Update to 9.8.20 (Latest) doesn't help...

Re: disconnection from network

Have you tried setting the ports to "access" or "host"? This will stop the port from trunking.

Community Member

Re: disconnection from network

I use "switchport access vlan xxx"

I don't use TRUNKING at HOST ports.

Re: disconnection from network

I suspect that your Computer NIC supports trunking. I believe that the default trunk configuration on the 3550 switch is "dynamic desirable", therefore if the NIC tries to setup a trunk the switch will comply.

If you run the command "switchport mode access" on the swith interface, it will rule this out as a possibility.

You might also want to run "no switchport nonegotiate" to turn off Dynamic Trunking Protocol (DTP)

Community Member

Re: disconnection from network


Just wondering if anybody came up with anything further regarding this issue?



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