Great Scott Gadgets Throwing Star LAN Tap Kit, Instructions

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Usage
1. Use Ethernet cables to connect the
Throwing Star LAN Tap (J1 and J2) in line
with a target network to be monitored.
2. Use Ethernet cables to connect one or both
of the monitoring ports (J3 and J4) to ports
on one or two monitoring stations. Each port
monitors traffic in one direction only.
3. Use your favorite software (e.g., tcpdump
or Wireshark) on the monitoring station(s) to
capture network traffic.
More Information
The Throwing Star LAN Tap is a passive Ethernet tap, requiring no power for operation. There are active
methods of tapping Ethernet connections (e.g., a mirror port on a switch), but none can beat passive taps for
portability. To the target network, the Throwing Star LAN Tap looks just like a section of cable, but the
wires in the cable extend to the monitoring ports in addition to connecting one target port to the other.
The monitoring ports (J3 and J4) are receive­only; they connect to the receive data lines on the monitoring
station but do not connect to the station's transmit lines. This makes it impossible for the monitoring station
to accidentally transmit data packets onto the target network.
The Throwing Star LAN Tap is designed to monitor 10BASE­T and 100BASE­TX networks. It is not
possible for an unpowered tap to perform monitoring of 1000BASE­T (Gigabit Ethernet) networks, so the
Throwing Star LAN Tap intentionally degrades the quality of 1000BASE­T target networks, forcing them
to negotiate a lower speed (typically 100BASE­TX) that can be passively monitored. This is the purpose of
the two capacitors (C1 and C2).
Like all passive LAN Taps, the Throwing Star LAN Tap degrades signal quality to some extent. Except as
described above for Gigabit networks, this rarely causes problems on the target network. In situations where
very long cables are in use, the signal degradation could reduce network performance. It is a good practice
to use cables that are not any longer than necessary.
Theory of Operation
For open source design files and additional information, including the most recent version of this document,
visit:
http://greatscottgadgets.com/throwingstar/
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