Is this port supposed to support full duplex? I'm running 8.3(3) and I get an error saying that full duplex isn't supported on this port. When I do a show port capabilites, it says that only half duplex is supported. Is there something I'm missing?

There is an internal bug for this issue

CSCef54418

Sup720 uplink 5/2 failed to set duplex with 10/100 speed.

Fix will be in 8.4(x) expected during end of October

Thanks! That's exactly what I was looking for. I appreciate the detailed, fast response.

I've got two 6509's running 8.3(3) connected via the Sup720 5/2 ports, both set as media type RJ45. One is forced to full/1000, and the other is set to auto/auto. The full/1000 side is running full/1000, and the auto/auto side is running a-full/a-1gb. Showing port capabilities does report each port as only capable of half duplex. Is the 'show port' command incorrectly reporting the ports running at full duplex?

Thats part of the problem. It can do full duplex but reports it can do half duplex in sh port capabilities.