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Ethernet Statistics

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Ethernet Statistics

Information about Receive Errors and Transmit Errors is displayed in this window. Information that cannot be obtained from the hardware or support software is indicated by N/A.

  • Receive Errors

    • Total Errors - displays the number of Ethernet errors received on this interface. The count includes alignment errors, FCS errors, frames that were too long, and MAC receive errors. This value is for total errors received on the interface. Since you may have multiple interfaces on one NIC, this value may not represent the total number of errors received by the NIC.

      If the item is 0, the total errors received may be 0, or this item cannot be obtained from the hardware or support software.

    • Alignment Errors - displays the number of alignment errors that have occurred for this interface since the network interface supporting software was loaded. The alignment of a frame is checked by the receiver after the packet has failed the Cyclical Redundancy Check (CRC). Misaligned packets do not end on an 8-bit boundary. All packets contain a set number of bytes and must end after a defined number of bytes. Packets that do not end on a byte boundary fail the alignment check.

      OID: 1.3.6.1.2.1.10.7.2.1.2 - dot3StatsAlignmentErrors

    • FCS Errors - lists the number of FCS (Frame Check Sequence) errors that have occurred for this interface since the network interface supporting software was loaded. The FCS field contains a 4-byte Cyclic Redundancy Check (CRC) value. The transmitting station calculates the CRC while sending the packet. The CRC value is placed in the FCS field. The receiving station calculates the CRC while receiving the packet and matches the resulting value against the contents of the FCS field. If the numbers do not match, an FCS error has occurred.

      Track and resolve these errors. The two primary causes of FCS errors are cabling and component problems.

      If you receive FCS Errors, check to see whether you have Alignment errors or Late Collision errors. Cabling problems, such as shorts or noise caused by electromagnetic interference, are most likely to blame for CRC/Alignment errors. Improper cabling (not following cable specifications) is the most likely cause for late collisions.

      OID: 1.3.6.1.2.1.10.7.2.1.3 - dot3StatsFCSErrors

    • Frame Too Long - displays the number of times a receiving station found an oversized frame for this interface since the network interface supporting software was loaded. To avoid processing corrupt packets, the receiving station checks several packet characteristics, including the frame size. If a frame is larger than 1518 bytes (including the FCS field), it is considered oversized. If the network is experiencing oversized frames, perform the following steps:

      1. Ensure you have the latest revision of the LAN driver. Oversized frames may be caused by a faulty LAN driver.

      2. Check your routers. If a router connects two dissimilar network types and does not enforce the proper frame size restrictions on either side, it may transmit illegal-length frames. Check with the router manufacturer.

      3. Use a network analyzer to find the NIC responsible for sending illegal-length frames. Examine the 48-bit source address in the frame header; this will pinpoint the responsible NIC.

      OID: 1.3.6.1.2.1.10.7.2.1.13 - dot3StatsFrameTooLongs

    • MAC Received Errors - increments each time an error occurs for this interface that does not fall into any of the other error categories shown on the screen. For example, this item increments if a frame that is too short is detected. If you see an excessive number of these errors, use a network analyzer to check for short frame errors. The NIC may need to be replaced.

      OID: 1.3.6.1.2.1.10.7.2.1.16 - dot3StatsInternalMacReceiveErrors

  • Transmit Errors

    • Total Errors - displays the total number of Ethernet errors generated from this interface. This count includes carrier sense errors, late collisions, excessive collisions, MAC transmit errors, multiple collision frames, single collision frames, and deferred transmits. This value is for total errors transmitted on the interface. Since you may have multiple interfaces on one NIC, this value may not represent the total number of errors transmitted by the NIC.

      If the item is 0, the total errors transmitted may be 0 or this item cannot be obtained from the hardware or support software.

    • Carrier Sense Errors - displays the number of frames transmitted with carrier sense errors for this interface since the network interface supporting software was loaded. The carrier sense signal is an ongoing activity of a data station that detects whether another station is transmitting. Carrier sense errors are detected when a station transmits a frame and does not detect its own signal on the wire.

      OID: 1.3.6.1.2.1.10.7.2.1.11 - dot3StatsCarrierSenseErrors

    • Late Collisions - displays the number of late collisions that have occurred for this interface since the network interface supporting software was loaded. Late collisions may be a symptom of cabling problems. A late collision is one that occurred 64 bytes or more into the packet.

      Late collisions may be an indication that a segment is longer than allowed by the wiring specifications. For example, if you are using 10Base-2 wiring, also known as Thinnet, the maximum segment length is 185 meters.

      A station will believe it has control of the cable segment if it has already transmitted 64 bytes. If another node at the far end of the segment has not yet seen the packet, and transmits, this packet will collide with the first transmission after the first 64 bytes have been sent.

      Ensure that your segment length does not exceed the maximum length allowed.

      Because the location of cabling problems can be very difficult to detect on an Ethernet network, shorten an Ethernet segment (remove portions of the network to isolate problems) until the problems are no longer seen, and then expand the network until the problem recurs.

      OID: 1.3.6.1.2.1.10.7.2.1.8 - dot3StatsLateCollisions

    • Excessive Collisions - displays the number of Excessive Collisions that have occurred for this interface since the network interface supporting software was loaded. A station may attempt to transmit up to 16 times before it must abort the attempt. Once the abort occurs, this counter increments.

      If you see an increase in deferred transmissions as well as excessive collisions, your network is extremely busy and this segment of the LAN is overcrowded. Reduce the traffic by reorganizing your LAN or adding a NIC to the device. For example, if you have 100 stations on one Ethernet bus, you may want to break it into two Ethernet buses by adding a NIC to your device. In this way you can balance the load by putting 50 stations on one bus and 50 on the other. If there are a few isolated stations creating the traffic, put those stations on a separate bus.

      Faulty components may be the cause of excessive collisions.

      OID: 1.3.6.1.2.1.10.7.2.1.9 - dot3StatsExcessiveCollisions

    • MAC Transmit Errors - increments each time an error occurs for this interface that does not fall into any of the other error categories shown on the screen. An excessive number of MAC Transmit errors may indicate a problem with the NIC. Check the cabling or replace the NIC.

      OID: 1.3.6.1.2.1.10.7.2.1.10 - dot3StatsInternalMacTransmitErrors

    • Multiple Collision Frames - displays the number of multiple collisions that have occurred for this interface since the network interface supporting software was loaded. Multiple collisions are frames involved in more than one collision before being successfully transmitted. These errors mean that the network is experiencing moderate to heavy traffic. If multiple collisions become more frequent, the count for excessive collisions escalates.

      OID: 1.3.6.1.2.1.10.7.2.1.5 - dot3StatsMultipleCollisionFrames

    • Single Collision Frames - displays the number of single collisions that have occurred for this interface since the network interface supporting software was loaded. Single collisions are frames that are involved in a single collision and then are transmitted successfully. These errors show that the network has light to moderate traffic. If single collisions become more frequent, the count for multiple collisions escalates.

      OID: 1.3.6.1.2.1.10.7.2.1.4 - dot3StatsSingleCollisionFrames

    • Deferred Transmits - displays the number of frames that were deferred before transmission because the medium was busy. These are deferred transmissions for this interface since the network interface supporting software was loaded. Frames involved in collisions are not counted, but frames that wait before transmission are counted.

      Deferred transmissions occur when the network is extremely busy. High counts of multiple collisions and excessive collisions also occur.

      Deferred transmissions indicate that this segment of the LAN is overcrowded. Reduce the traffic by reorganizing the LAN. For example, if you have 100 stations on one Ethernet bus, break the bus into two Ethernet buses by adding a NIC to your device. This balances the load by putting 50 stations on one bus and 50 on the other. If a few isolated stations create the traffic, put them on a separate bus.

      OID: 1.3.6.1.2.1.10.7.2.1.7 - dot3StatsDeferredTransmissions

Related Topics

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