You can use the UNIX ethtool command. Login as admin and su to root. Then, you can run ethtool against any interface (typically named eth0, eth1, etc.):
root@bmhavautl:/home/admin/#: ethtool eth0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
Advertised auto-negotiation: Yes
Port: Twisted Pair
Supports Wake-on: umbg
Current message level: 0x00000003 (3)
Link detected: yes
You'll note my interface above is running at 1Gbps, full-duplex.
Let us know if that helps!