System information

Troubleshooting Ethernet 4-63
show interfaces ethernet Field Descriptions
Five minute input rate,
Five minute output rate
Average number of bits and packets transmitted per second in the past five minutes. If the
interface is not in promiscuous mode, it senses network traffic it sends and receives
(rather than all network traffic).
The five-minute input and output rates should be used only as an approximation of traffic
per second during a given five-minute period. These rates are exponentially weighted
averages with a time constant of five minutes. A period of four time constants must pass
before the average will be within 2 percent of the instantaneous rate of a uniform stream
of traffic over that period.
packets input Total number of error-free packets received by the system.
bytes input Total number of bytes, including data and MAC encapsulation, in the error-free packets
received by the system.
no buffers Number of received packets discarded because there was no buffer space in the main
system. Compare with ignored count. Broadcast storms on Ethernet networks and bursts
of noise on serial lines are often responsible for no input buffer events.
Received...broadcasts Total number of broadcast or multicast packets received by the interface.
runts Number of packets that are discarded because they are smaller than the medium's
minimum packet size. For instance, any Ethernet packet that is less than 64 bytes is
considered a runt.
giants Number of packets that are discarded because they exceed the medium's maximum
packet size. For example, any Ethernet packet that is greater than 1,518 bytes is
considered a giant.
input error Includes runts, giants, no buffer, CRC, frame, overrun, and ignored counts. Other
input-related errors can also cause the input error count to be increased, and some
datagrams may have more than one error; therefore, this sum may not balance with the
sum of enumerated input error counts.
CRC Cyclic redundancy checksum generated by the originating LAN station or far-end device
does not match the checksum calculated from the data received. On a LAN, this usually
indicates noise or transmission problems on the LAN interface or the LAN bus itself. A
high number of CRCs is usually the result of collisions or a station transmitting bad data.
frame Number of packets received incorrectly having a CRC error and a noninteger number of
octets. On a LAN, this is usually the result of collisions or a malfunctioning Ethernet
device.
overrun Number of times the receiver hardware was unable to hand received data to a hardware
buffer because the input rate exceeded the receiver's ability to handle the data.
ignored Number of received packets ignored by the interface because the interface hardware ran
low on internal buffers. These buffers are different from the system buffers mentioned
previously in the buffer description. Broadcast storms and bursts of noise can cause the
ignored count to be increased.
input packets with dribble
condition detected
Dribble bit error indicates that a frame is slightly too long. This frame error counter is
incremented just for informational purposes; the router accepts the frame.
packets output Total number of messages transmitted by the system.
bytes Total number of bytes, including data and MAC encapsulation, transmitted by the
system.
underruns Number of times the transmitter has been running faster than the router can handle. This
may never be reported on some interfaces.
output errors Sum of all errors that prevented the final transmission of datagrams out of the interface
being examined. Note that this may not balance with the sum of the enumerated output
errors, as some datagrams may have more than one error and others may have errors that
do not fall into any of the specifically tabulated categories.
Field Description