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New Member

3508G XL GbE + Compaq NC7131: crossover cables?

Having some troubles with (I think) the auto-sensing crossover state functionality of Compaq's 10/100/1000 NIC.

We have five identical Proliant 1600 servers - each with a new NC7131 Gigabit over copper NIC. The switch is a New Catalyst 3508G XL with GbE GBICs. NIC Drivers are from SmartStart 5.20. NOS is NT4 at SP6.

Server to Server with crossover cable works.

Server to Server with normal cable works.

Server to switch with crossover cable works.

Switch port to switch port with crossover cable works (link status LEDs indicate 1000 Full duplex).

Server to switch with normal cable doesn't work!

We've tried forcing the NIC parameters (1000, Full Duplex), but this makes no difference. This NIC connects to 100 Mb/s ethernet switch ports OK using a normal straight though cable. I haven't found a way to disable the NIC's autosense crossover state.

Cisco literature says that the GBIC GbE ports don't auto-sense crossover and that they're set to crossover (as a normal switch would be).

I think the switch is OK (it works when we connect the servers with crossover cables). We can probably make all this work by buying 5 crossover patch cables. Anyone have a better idea?


Dennis Watson

New Member

Re: 3508G XL GbE + Compaq NC7131: crossover cables?


What type of cross-over cable are you using? If it is a standard CAT 5 cross-over cable you will only get 100Mb NOT 1000Mb for Gigabit over Copper uses all 8 wires.

We use between a 3550-12T (10*1000baseT + 2 GBIC ports) and other switches with a GBIC-T a straight cable which indicates to me that the GBIC is auto-negotiating for when we connect 2 GBIC's togehter with the same straight cable they also work.

Be sure that the patch leads are of good quality and preferably CAT5E.

Hope it helps you a bit on the way, Maarten Sjouw.

New Member

Re: 3508G XL GbE + Compaq NC7131: crossover cables?

Thanks for your reply, Maarten.

To reiterate, we are now successfully using a crossover cable to connect the server's NIC and the Gb Ethernet GBIC on the 3508G XL. As you say, the crossover is using all 8 wires in the cable to connect at 1000 Mb/s Full Duplex.

Seems to me though, that we ought to be able to make this connection using a STRAIGHT THROUGH Cat5e cable to connect the server to the switch port... That's the way it works in the 10BaseT and 100BaseT world that I'm more familiar with.


Dennis Watson

New Member

Re: 3508G XL GbE + Compaq NC7131: crossover cables?

Well, Dennis,

I would say you're completely right, but...

Most of the times technology does not do what we expect or what the engineers thought it would do, as I was trying to get etherchannel running using 2 GB ports to another 3500 switch, according to the manuals it should be possible, but it just does not work, it just puts the network to a halt.

I think your best bet is to keep using cross-over cables for now.

Regards, Maarten Sjouw.