The LED configuration for the GS45 LAN ports are based on the diagrams in the Intel 82579 User’s manual. (see the link below). The reference diagram is on page 239 of this manual.
There is a 300-ohm current limiting resistor in the reference diagram. The ADLGS45PC has a built-in 330-ohm resistor for both the SPEED100 and LINKACT signal lines. For those 2 LAN indicators, it’s possible to just wire in the appropriate LED to the signal pin at one end, and the other end to the 3.3V power at pin12 and you’re done.
The SPEED1000 LED (pin 7) does NOT have the 330-ohm inline resistor, and this is different from the other two signals (I’m not sure why). If you plan on using that LAN LED, you may need to add one in your design.