Chapter 10: Troubleshooting
The default ping generates approximately one 64-byte packet per second. This is not a robust test. If
convenient, locate a ping program or set command line parameters to generate perhaps 50 pings per second
and try both small packets and large 1400-byte packets. Be aware that packets larger than 1400 bytes
sometimes uncover bugs in the software of ping programs.
Step-by-Step Diagnosis
This section assumes that communication between two machines at opposite ends of the E3, T3/DS3 link
(herein the link) is failing. If this is a test in the laboratory or without a telecom link present, be sure to read
the previous “Laboratory Testing” section first.
1. If access to the HTTP management interface of the converter is possible, many useful status messages
will be displayed. Typically, any message highlighted in orange should be of concern. Error counters
are of lesser concern if they are not incrementing, and some link errors would be normal as link cables
are initially connected.
2.
The DS3/E3
BER
light of the converter should be illuminated and green
. This indicates that a valid,
DS3/E3 waveshape is being received without bit errors and with proper framing. Refer to the front
panel section of this document for other light colors.
The DS3/E3
port
light of the converter should be illuminated and green
. This indicates that a valid,
framed carrier signal and sync is being received from a remote E3Switch converter. Refer to the front
panel section of this document for other light colors.
If orange, data will not be received by the local converter and the loss of data is occurring on the link
between the converters. Check that the incoming circuit ID shown at the top of the converter's HTTP
management page matches the circuit ID being transmitted by the remote converter as shown at the
remote converter's HTTP management settings page (only applies if framing is C-Bit DS3 and
firmware since November 2009 exists in units at each end of the link).
If flashing orange/green, the link may be in loopback as indicated by the HTTP management status
page. If not in loopback,, the
remote
unit is not receiving a valid sync from the local unit. Check the
TX path starting at the local unit. Ensure the carrier believes the link is set up in unchannelized mode
(not subdivided into T1 or E1 channels). Either M13 or C-Bit framing is fine but the configuration
page setting of each converter should match and the carrier should have consistent framing settings on
intermediate equipment – not mixed among M13 and C-Bit or autoconfigure.
If flashing orange/black, the link is in a configured return-to-service delay mode as discussed
elsewhere.
3.
Ensure a proper LAN cable is being used
. Straight-through or crossover cabling is acceptable. The
LAN light of the converter port to which any LAN is attached should be illuminated and green. If not,
ensure that the attached equipment is set for autonegotiation and can accept 100BaseTX Full-Duplex
links. Refer to front panel section of this document for other LAN light colors.
4. The network equipment attached to the LAN port of the converter should be set for autonegotiation
mode in order to allow the converter to negotiate a 100Mbit full-duplex connection. Forcing either the
converter's or attached equipment's LAN port to 100Mbit full-duplex may not allow the proper
autonegotiation and LAN connection to occur. There are rare cases with older LAN equipment in
which it may be necessary to disable autonegotiation.
If crc-errors or short packet errors are seen
in the management statistics of the LAN port, the attached LAN equipment has probably
configured itself to half-duplex mode and colliding packets are being lost
. In such a case,
autonegotiation should be disabled on
both
the converter and the attached LAN equipment with both
forced to 100BaseTX full-duplex. Autonegotiation interoperability and standards were not well
understood by the industry at the inception of 100BaseTX, resulting in some older LAN equipment not
understanding the converter's autonegotiation advertisement of strictly full-duplex capability.
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