Installation guide

C HAPTER 7
How dongles work
Dongles, included with all 10/100-port McAfee
®
Network Security Sensors (Sensors), are
required when a 10/100 Sensor port runs in SPAN or inline fail-closed mode.
All 10/100 ports on the Sensors are standard 10/100 Base-T Ethernet ports. As such, they
make use of only 4 of the 8 wires in a Category 5/6 twisted pair cable:
Pin Function
1 Tx
2 Tx
3 Rx
4
5
6 Rx
7
8
Pins 1 and 2 are used to transmit (Tx) signals, pins 3 and 6 are used to receive (Rx)
signals, and pins 4, 5, 7, and 8 are not used.
When a port pair operates in inline fail-open mode, the signals are “crossed” to allow for
the normal flow of traffic:
Figure 5: Inline fail-open mode - Signals crossed
In this way, traffic that is received on the Rx pins on one port are sent on the Tx pins on
the other port.
Note: This is the same cross performed by a crossover cable.
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