HP J4091A Installation And Reference Manual page 26

HP 100Base-T Hub 8 Installation and Reference Guide
Troubleshooting: If the Link LED does not light up when a device is connected to its
corresponding port, check that both the hub and connected device are powered on.
Check that the cable length does not exceed 100 meters. You should have standard,
straight-through cables and not crossover or other specialized cables.
Partition
Color: Yellow
Function: Detects that a port was disabled because of bad packets being
passed
Condition
ON Hub has disabled the port because of excessive collisions detected at the port.
OFF Hub port is enabled.
A port is temporarily partitioned when a line error or too many collisions
are detected on the attached segment. While it is automatically partitioned,
the port continues to receive data from the segment. However, data is not
transmitted onto the segment. When the problem is corrected or a valid
data packet is received through the port, the port is automatically
reconnected. When partitioning occurs, the port's corresponding Partition
LED will be continually lit (yellow light). Otherwise, this LED should be
OFF (unlit).
Note: When a long run of collisions occur on the cable connected to a hub port (i.e.,
64 collisions), that port is automatically partitioned by the hub. It is
automatically reconnected when a collision-free data packet at least 512 bits
long (i.e., a minimum size legal packet) passes through the port.
4-4
Indication
Hardware Reference