Juniper ACX1000 Configuration Manual page 1387

Copyright © 2017, Juniper Networks, Inc.
Chapter 36: Diagnosing Cable States Using Time Domain Reflectometry (TDR)
While measuring the cable length or distance to fault (per pair), sometimes, a few
cable length inconsistencies might be observed during a TDR test. Broadcom
transceivers have the following cable length limitations:
For a properly-terminated good cable, the accuracy of the cable length reported is
plus or minus 10 meters.
If a pair is open or short-circuited, the far-end termination does not affect the
computed result for that pair.
The accuracy of the measured cable length, when open and short-circuit conditions
are detected, is plus or minus 5 meters.
The accuracy of a good pair, when one or more pairs are open or short-circuited, is
plus or minus 10 meters.
Polarity swap detection is supported only in 10BASE-T mode.
The TDR test does not impact the traffic if the interface operates at 10-Gigabit Ethernet
per second of bandwidth, which is the default configuration. However, if the speed of
the interface is configured to be other than 10-Gigabit Ethernet, running the TDR test
affects the traffic.
TDR diagnostics might bring the link down and initialize the physical layer (PHY) with
default configuration to perform its operation.
When the TDR validation test is completed, the PHY layer resumes operation in the
same manner as before the cable diagnostics test was performed. However, link flaps
might be momentarily observed. We recommend that you run the TDR test at a speed
of 1 gigabit per second, which is the default configuration, to obtain more accurate
results.
TDR is supported on the following interfaces on ACX Series routers:
On ACX1000 routers, 4 RJ45 (Cu) ports or 8-port Gigabit Ethernet MICs with small
form-factor pluggable (SFP) transceivers and RJ45 connectors.
On ACX1100 routers, 4-port or 8-port Gigabit Ethernet MICs with SFP transceivers and
RJ45 connectors.
On ACX2000 routers, 8-port Gigabit Ethernet MICs with SFP transceivers and RJ45
connectors.
On ACX2100 and ACX2200 routers, 4-port Gigabit Ethernet MICs with SFP transceivers
and RJ45 connectors.
On ACX4000 routers, 4-port, 6-port, or 8-port Gigabit Ethernet MICs with SFP
transceivers and RJ45 connectors.
You must select the media type as copper for the 1-Gigabit Ethernet interfaces. To specify
the media type, include the
interfaces interface-name]
in slot 2. When media-type is not set, the port accepts either type of connection. The
media type is fiber if a transceiver is installed in the SFP connection. If no transceiver is
installed, the media type is copper. The COMBO ports (combination ports) on ACX routers
statement with the
media-type
hierarchy level. Media type selection is applicable to ports only
option at the
copper [edit
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