Port Details: Faults

Rx short errors
Function: Shows the number of frames received that were shorter than minimum collision fragments.
Significance: Shorts can be caused by noisy connections, cable faults and faults in network hardware. If they occur often, remedial action should be taken.

Rx CRC errors
Function: Shows the number of frames received on the port that have been corrupted during transmission. A CRC error is registered when the 4-byte checksum is invalid, that is the CRC information in the frame does not match the CRC computed by the receiving station.
Significance: The frame will be discarded. Re-transmission by a higher-level protocol is required. CRC errors are usually caused by cable faults and faults in network hardware.

Rx alignment errors
Function: Shows the number of frames received that have an alignment error. Alignment errors are frames that are longer than 64 bytes, have a bad CRC and are not an integral number of bytes in length;-that is; the number of bits in the frame is not divisible by 8.
Significance: Frames with alignment errors are discarded. Too high a proportion of alignment errors will severely affect performance because the dropped frames have to be retransmitted by higher-level protocols. Alignment errors are usually caused by cable or transceiver faults.

Rx long errors
Function: Shows the number of frames that are longer than the legal maximum length of 1518 bytes but shorter than 6000 bytes.
Significance: Longs can affect general performance and may result in users being disconnected. The station transmitting the oversized frames has a hardware or software error. It should be found and removed from the network.

Rx very long errors
Function: Shows the number of times that a frame longer than 6000 bytes (also called "giants") has been received.
Significance: See "Rx long errors" above.

Rx jabber errors
Function: A jabber is a long frame with a CRC or alignment error.
Significance: See "Rx long errors" above.

Rx code violation errors
Function: Shows the number of illegal codes received by the port.
Significance: When using 100 Mbps links, each 4-bit code is transferred on the wire as a 5-bit code. This creates some illegal codes that should never be sent; if they are sent, they are received and discarded as Code violations.

Rx overrun drops
Function: Shows there are more packets received than can be buffered.
Significance: The packet is then discarded.

Rx out of pools
Function: Shows there are no memory pools left because there are so many frames stored.
Significance: The port tries to cause collisions to increase the number of frames rejected; this gives the pools time to empty.

Rx 2nd port drops
Function: Shows the number of packets discarded due to a MAC address moving to a new port before its old filter entry has aged out.
Significance: The packet is discarded and the new position of the MAC address is learned.

Rx illegal MAC address drops
Function: Detects illegal source MAC addresses and discard them and count them.
Significance: IP multicast sources and 0.0.0.0 values are not allowed on the network. They are not forwarded and are dropped.

Rx unsupported MAC frames
Function: Number of unsupported MAC control frames.
Significance:

Tx deferreds
Function: Shows the number of times the transmission of a frame is postponed due to another frame already being transmitted on the Ethernet network.
Significance: This is a normal event on an Ethernet network. A high number of deferred transmissions usually indicates good use of the bandwidth for the network segment.

Tx packets without link
Function: Shows the number of packets that have been sent without a link.
Significance: If a cable is removed from a port, some packets are lost before the port is shut down (by the software). If a very large number of packets is measured, this may indicate a problem with the software in the switch.

Link down events
Function: Shows the number of times that link pulses have failed to be detected.
Significance: Usually, this means that there are faults on the cable or that the cable has been removed.


More info about

Port colors

Flow control

Configuring port mirroring


Procedures

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