Intel 82541GI NIC comes up at 10mbps on one port

Sam Varshavchik mrsam at courier-mta.com
Sun Aug 17 20:16:43 UTC 2008


I'm stumped. I've got a motherboard with the following dual-port NIC:

03:0a.0 Ethernet controller: Intel Corporation 82541GI Gigabit Ethernet Controller
	Subsystem: Intel Corporation PRO/1000 MT Network Connection

One port is connected to my DSL modem. It comes up at 100mbps:

Aug 17 15:54:41 headache kernel: e1000: eth0: e1000_watchdog: NIC Link is Up 
100 Mbps Full Duplex, Flow Control: RX

The second port is connected to a plain-vanilla Linksys router. That port 
always negotiates to 10mbps, no matter what:

Aug 17 15:54:41 headache kernel: e1000: eth1: e1000_watchdog: NIC Link is Up 
10 Mbps Full Duplex, Flow Control: RX/TX

* Other machines have no problems talking to the Linksys router at 100mbps.

Things that I've already tried:

* Swapped the cables. Swapped the DSL cable with the router cable. The 
router port still comes up at 10mbps, the DSL port still comes up at 
100mbps. This proves that both cables can handle 100BaseT.

* Switched the ports on the motherboard. Switched the DSL port with the 
router port, using same cables (swapped the IP addresses on eth0 and eth1). 
The new router port (former DSL port) still comes up at 10mbps, the new DSL 
port (former router port) comes up at 100mbps. This proves that both ports 
can handle 100BaseT.

* Switched the ports on the Linksys router. Switched the port on the router 
with the port connected to another machine, that comes up at 100mbps. The 
other machine comes up at 100mbps on the port that this Intel NIC negotiates 
down to 10. This proves that all ports on the router can handle 100BaseT.

* Disconnected all machines from the router. Plugged back only this one, 
still comes up at 10mbps. This eliminates the possibility that the router 
can't handle all ports @100mbps.

* Disconnected both the DSL cable and the router cable. Plugged in the 
router cable. The router cable still comes up at 10mbps. This eliminates the 
possibility that the motherboard cannot handle both ports @100mbps.

I've arrived at a dead end. No matter what, the motherboard can talk to the 
router only @10mbps. The only possibility that I see is that the 'Intel 
Corporation 82541GI' NIC has an interoperability problem with this specific 
Linksys router hardware. It's a plain blue 5-port consumer router, plug in 
and go, no knobs to turn.

So, any suggestions, besides "get a new router"?


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