You have to use mii-tool to set the speed of your NIC.
Just a the line that appley to you in /etc/rc.d/rc.local file.
mii-tool -F 100baseTx-HD eth0
mii-tool -F 100baseTx-FD eth0
mii-tool -F 10baseT-HD eth0
mii-tool -F 10baseT-FD eth0
Or
For example:
Assuming we are using the eepro100 driver you need to make the following entries in /etc/modules.conf
alias eth0 eepro100
options eepro100 options=0x30
The various options are:
Hex Decimal Meaning
0x10 16 Force Full-Duplex operation (must be used with 0x20 or 0x40)
0x20 32 Force 100mbps-only operation
0x30 48 Force 100mbps-only with Full Duplex
0x40 64 Force 10mbps-only
0x50 80 Force 10mpps-only with Full Duplex
This information for a particular driver can usually be found in the doucmentation for that driver.