Information Technology Reference
In-Depth Information
Table15-9 Show Interfaces Serial Field Descriptions (continued)
Field
Description
input errors
Gives the total number of no buffer, runts, giants, CRCs,
frame, overrun, ignored, and abort counts. Other
input-related errors can also increment the count, so this
sum might not balance with the other counts.
CRC
The Cyclic Redundancy Check (CRC) counter is
incremented by the originating station or far-end device
when the checksum calculated from the data received
does not match the checksum from the transmitted data.
On a serial link, CRCs usually indicate noise, gain hits, or
other transmission problems on the data link.
frame
Gives the number of packets received incorrectly, having
a CRC error and a noninteger number of octets. On a
serial line, this is usually the result of noise or other
transmission problems.
overrun
Gives the number of times that the serial receiver
hardware was incapable of handing received data to a
hardware buffer because the input rate exceeded the
receiver's capability to handle the data.
ignored
Gives the number of received packets ignored by the
interface because the interface hardware ran low on
internal buffers. Broadcast storms and bursts of noise can
cause the ignored count to be increased.
abort
Indicates an illegal sequence of 1 bit on a serial interface.
This usually indicates a clocking problem between the
serial interface and the data link equipment.
carrier transitions
Gives the number of times that the carrier detect signal of
a serial interface has changed state. For example, if data
carrier detect (DCD) goes down and comes up, the carrier
transition counter will increment two times. This
indicates modem or line problems if the carrier detect line
is changing state often.
packets output
Gives the total number of messages transmitted by the
system.
bytes output
Gives the total number of bytes, including data and MAC
encapsulation, transmitted by the system.
underruns
Gives the number of times that the transmitter has been
running faster than the router can handle. This might
never be reported on some interfaces.
output errors
Gives the sum of all errors that prevented the final
transmission of datagrams out of the interface being
examined. Note that this might not balance with the sum
of the enumerated output errors because some datagrams
can have more than one error, and others can have errors
that do not fall into any of the specifically tabulated
categories.
