Realtek NIC on Powerconnect 6248 showing disconnected until power cycled

did you enable

spanning-tree portfast

on the network ports?

Which firmware version are you using?

Thilo

Here is some additional information on Portfast:

• Portfast Allows immediate transition to a forwarding state

• Port still participates in STP

• Used for non-switch devices

• Clients

• Servers

• Printers

• Prevents unnecessary timeouts from DHCP servers

• Portfast configuration ignored when port is connected to another switch

When a host is attached to a network switch such as a computer, printer or server, STP will run on the port. Forwarding state will occur, albeit after a delay of about 50 seconds while it goes through the listening and learning states.  

As STP is running, no user data will pass via the port. The host NIC is active however it has no network connectivity.  Some user applications can time out during the period, such as DHCP.  This would cause the host to self issue an Apipa address (169.254.x.x) this address will not allow the host to communicate on the network.

In order to allow immediate transition of the port into the forwarding state for Hosts, enable the STP PortFast feature. PortFast immediately transitions the port into STP forwarding mode upon linkup with less than a 5 sec delay. The port still participates in STP.  So if the port receives a BPDU from another Network bridge (switch), the port ignores PortFast and processes the BPDU as normal.  The port transitions through Listening, learning, forwarding or blocking state with the original 50 sec delay.  There is no danger of causing a data Loop as STP is always listening for BPDU’s with or without PortFast enabled on all ports.

It is highly recommend to enable PortFast on all client ports.  It is highly discouraged to Disable STP under any circumstances unless there is a specific reason to.  Without STP the switch will behave as an unmanaged switch!

To configure Portfast on an interface:

console# config

console(config)# interface ethernet g5  this command will vary depending on specific switch model

console(config-if)# spanning-tree portfast  this enables Portfast on this port

console(config-if)# exit

This firmware - PC6200v3.3.3.3 was just released 4/3/2012.

  http://www.dell.com/support/drivers/us/en/04/DriverDetails/DriverFileFormats?DriverId=53M6W&FileId=2923322702&productCode=powerconnect-6248&urlProductCode=False

Thanks for that great description of STP, I am using portfast on all ports except the uplinks to the main rack.  I have 1 switch running firmware 2.2.0.3 and 1 running 3.3.1.10 and they both have the same problem.  I am about to try removing the portfast command from the ports to see if that makes a difference to the connectivity.  Though the slow network startup time is an issue as we have network boot menu's that need to load and the students have to wait to login on the machine for the network to start.

Also will by updating the switch firmware tonight.

I have tried disabling portfast and have not been able to replicate the problem, however boot time is much greater and networking starts after windows has finished booting now, so some users have to wait to login if they have not to that machine before.

You misunderstood me, you should enable portfast on PC ports of course.

Did you try the latest NIC drivers from Realtek?

www.realtek.com.tw/.../downloadsView.aspx

I had a similar problem where the latest driver cured the problem.

Thilo