3Com 3C16751A manual Straight-through Cable/Crossover Cable

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	Uplink	Normal	Pin		Pin	Normal
port				port	port				port
Rx+		1	1	Rx-	Rx+		1	1	Rx+
		2	2				2	2
Rx-				Rx+	Rx-				Rx-
		3	3				3	3
Tx+				Tx-	Tx+				Tx+
		4	4				4	4
		5	5				5	5
Tx-		6	6	Tx+	Tx-		6	6	Tx-
		7	7				7	7
		8	8				8	8

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