3Com Hub User Manual page 15

Port Status LED flashing. The port is partitioned, probably
due to a network loop. Examine your connections and
remove the loop. Each piece of equipment needs only one
connection to your Hub.
Link between the Hub and another OfficeConnect hub
not working. Check your connections; follow the
information given in the "Connecting Another
OfficeConnect Hub" section on page 11. It is likely that an
Uplink/Normal switch is incorrectly set.
Port Status LED not lit for a port that has a
connection. Check that you are using a 'straight-through'
cable which is properly connected at both ends, and is not
damaged. Refer to "Twisted Pair (TP) Cables" on page 8.
Also check that the equipment connected to the Hub is
powered on, operating correctly and contains the correct
type of connection. Refer to Figure 6 to compare the wiring
of a straight-through and a crossover cable.
Figure 6 Straight-through Cable/Crossover Cable
Normal
Pin Pin
port
1
Rx+
2
Rx-
3
Tx+
4
5
6
Tx-
7
8
15
Uplink Normal
Pin
port port
1 1
Rx-
Rx+
2 2
Rx+
Rx-
3 3
Tx-
Tx+
4 4
5 5
6 6
Tx+
Tx-
7 7
8 8
Normal
Pin
port
1
Rx+
2
Rx-
3
Tx+
4
5
6
Tx-
7
8