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ManualsBrandsAllied Telesis ManualsSwitchAT-8700XL Series
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Hardware Reference 19
C613-03064-00 REV E
Loopback Plugs for Testing Switch Interfaces
Loopback plugs are used in conjunction with the Test Facility software to test
the physical interfaces on the switch (see the “Test Facility” section beginning
on page 22 of this Reference, and the Tes t Fa cil ity chapter of the AT-8700XL
Series Software Reference). The purpose of a loopback plug is to connect the
output pins on the interface to the input pins so that any data transmitted over
the interface is looped back and received at the same interface.
Gigabit copper interfaces (as found on the AT-A39/T uplink module) cannot be looped
back. Loopback plugs can only be used in conjunction with 10/100 Ethernet interfaces.
On interfaces with control signals, these are also looped back. The data
received on the interface is compared with the data transmitted to determine
whether or not the interface is functioning correctly. In order to produce a
comprehensive test report for the interface being tested, most tests performed
by the Test Facility require a loopback plug to be inserted.
Figure 8: Ethernet twisted pair (TP) loopback plug.
Test Facility
This section introduces the Test Facility. The Test Facility is built into all
AT-8700XL Series software. For detailed information on operating the Test
Facility, see the Test Facility chapter of the AT-8700XL Series Software
Reference.
The Test Facility is designed to test the switch’s physical interfaces. Testing
should not be performed while the switch is operational as the presence of a
loopback plug may cause feedback of network traffic. Also, any interfaces
being tested are dedicated to the Test Facility. The Test Facility can be thought
of as a specialised interface module like PPP or Frame Relay.
Test results are displayed with the command:
SHOW TEST
which produces a display like that shown in Figure 9 on page 20.
Not
connected
Not
connected
•Not
Twisted Pair (TP) Loopback Plug (RJ45 connector)
1
2
3
4
5
6
7
8
12345678
Switch end view
of plug
TX+
TX-
RX+
RX-
RTPLOOPsw