Dell Intel PRO Family of Adapters - Manual (Page 116)

The Intel® Ethernet 10G 4P X540/I350 rNDC and Intel® Gigabit 4P X540/I350 rNDC have the following indicator
lights:
Label Indication Meaning
LNK (green/yellow) Green on Operating at maximum port speed.
Yellow on Operating at lower port speed.
Off No link.
ACT (green) Green flashing Data activity.
Off No activity.
The Intel® Ethernet 10G 4P X520/I350 rNDC and Intel® Gigabit 4P X520/I350 rNDC have the following indicator
lights:
Label Indication Meaning
LNK (green/yellow) Green on Operating at maximum port speed.
Yellow on Operating at lower port speed.
Off No link.
ACT (green) Green flashing Data activity.
Off No activity.