I'm having an issue where some of my servers are not autonegotiating to the 1GB/s speed from their 1Gb NIC interfaces. These servers are Dell R610s running RHEL 5 wired to a Cisco switch. I have attempted to force the 1Gb speed from both the switch and server sides but have had no luck.
ethtool eth0 on the server provides shows that
1000baseT/Full is a "Supported link mode" and is part of the "Advertised link modes" as well.
I've tried to force the 1Gb interface by first running
ethtool -s eth0 autoneg off and then
ethtool -s eth0 speed 1000 duplex full. After running the second command I get the following errors:
Cannot set new settings: Invalid argument
not setting speed
not setting duplex
The previous commands will work if I try to force the speed to 100 instead of 1000. This has been puzzling me since we have other R610s which autonegotiate fine to the 1Gb speed.