Rockwell Automation 1734-AENTR EtherNet/IP Network Configuration User Manual - Manual (Page 127)

Rockwell Automation Publication ENET-UM001L-EN-P - March 2014 127
Troubleshoot an EtherNet/IP Communication Module with Diagnostic Web Pages Chapter 10
Rockwell Automation Publication ENET-UM001L-EN-P - March 2014 127
Troubleshoot an EtherNet/IP Communication Module with Diagnostic Web Pages Chapter 10
Ethernet Statistics
Your EtherNet/IP communication module may experience intermittent network
connectivity due to these conditions:
• Duplex mismatch
• Electrical noise induced into a cable or resulting from a Logix/switch
ground potential difference
• Bad hardware, such as a cable or switch part
Before troubleshooting this problem, familiarize yourself with these Ethernet
statistics, or media counters.
Media Counter Definition
Alignment Errors A frame containing bits that do not total an integral multiple of eight.
Alignment errors often result from:
• starting or stopping of module.
• MAC-layer packet formation problems.
• cabling problems that corrupt or eliminate data.
• packets passing through more than two cascaded multiport transceivers.
FCS Errors A frame containing eight bits, at least one of which has been corrupted.
FCS errors often result from these conditions:
• Starting or stopping the module
• Cabling problems that corrupt data
Important: Even though the acceptable Ethernet bit-error rate is 1 in 108, the typical rate is 1 in 1012 or better.
Single Collisions The number of outgoing packets that encountered only one collision during transmission.
Multiple Collisions The number of outgoing packets that encountered 2...15 collisions during transmission.
SQE Test Errors A test to detect the collision-present circuit between a transceiver and a network interface card (NIC).
Important: Because most NICs now have an integrated transceiver, the SQE test is unnecessary. Ignore this media counter.
Deferred Transmissions The number of outgoing packets whose transmission is deferred because the network is busy when the first attempt is made to send them.
Important: The module will only defer the first attempt to transmit a packet. After the first attempt, the module will transmit the packet without
checking. However, if the network is still busy, a collision will be recorded.
Late Collisions The number of times two devices transmit data simultaneously.
Neither device detects a collision because the time it takes to send the signal from one end of the network to the other exceeds the time needed to put the
entire packet on the network. Consequently, neither device senses the other’s transmission until the entire packet is out on the network.
Late collisions often result from these conditions:
• Excessive network segment length
• Repeaters between devices
Important: Large and small packets can be affected by late collisions. However, the transmitter cannot detect late collisions between small packets.
Consequently, a network that experiences measurable late collisions between large packets will also lose small packets.
Excessive Collisions The number of frames that experience 16 consecutive collisions.
MAC Transmit Errors The number of frames for which transmission via a particular interface fails due to an internal MAC sublayer transmission error.
Important: MAC transmit errors are only counted if either late collisions, excessive collisions, or carrier sense errors are not counted.
MAC Receive Errors The number of frames for which reception via a particular interface fails due to an internal MAC sublayer transmission error.
Important: MAC receive errors are only counted if the frame too long count, alignment errors, or FCS errors are not counted.
Carrier Sense Errors Carrier sense errors fall into these categories:
• No Carrier Sense Present - The number of times the carrier is not present when a transmission starts.
• Carrier Sense Lost - The number of times the carrier is lost during a transmission.
Carrier sense errors usually indicate a problem with a cable on the Ethernet infrastructure.
Frame Too Long The number of incoming packets that exceed the maximum Ethernet packet size.