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Ethernet Port FAQ
Understanding SHOW INTERFACE FASTETHERNET stats
Posted: 30 Nov 01 (Edited 31 May 02)
FastEthernet0/0 is up
Indicates whether the interface hardware is currently active and if it has been taken down by an administrator.
line protocol is up
Indicates whether the software processes that handle the line protocol consider the line usable or if it has been taken down by an administrator.
Hardware is AmdFE, address is xxxx.xxxx.xxxx
Hardware type (for example, MCI Ethernet, SCI, cBus Ethernet) and MAC address.
MTU 1500 bytes
Maximum Transmission Unit of the interface.
BW 100000 Kbit
Bandwidth of the interface in kilobits per second.
DLY 100 usec
Delay of the interface in microseconds.
Reliability of the interface as a fraction of 255 (255/255 is 100% reliability), calculated as an exponential average over 5 minutes.
txload 1/255, rxload 1/255
Load on the interface as a fraction of 255 (255/255 is completely saturated), calculated as an exponential average over 5 minutes.
Encapsulation method assigned to interface.
loopback not set
Indicates whether loopback is set or not.
Keepalive set (10 sec)
Indicates whether keepalives are set or not.
Full-duplex, 100Mb/s, 100BaseTX/FX
Speed, Data Speed, and Wire Type
ARP type: ARPA
Type of Address Resolution Protocol assigned.
ARP Timeout 04:00:00
Number of hours, minutes, and seconds an ARP cache entry will stay in the cache.
Last input 00:00:01
Number of hours, minutes, and seconds since the last packet was successfully received by an interface. Useful for knowing when a dead interface failed.
Number of hours, minutes, and seconds since the last packet was successfully transmitted by the interface. Useful for knowing when a dead interface failed.
output hang never
Number of hours, minutes, and seconds (or never) since the interface was last reset because of a transmission that took too long. When the number of hours in any of the "last" fields exceeds 24 hours, the number of days and hours is printed. If that field overflows, asterisks are printed.
Last clearing of "show interface" counters 00:00:02
Time at which the counters that measure cumulative statistics (such as number of bytes transmitted and received) shown in this report were last reset to zero. Note that variables that might affect routing (for example, load and reliability) are not cleared when the counters are cleared. *** indicates the elapsed time is too large to be displayed. 0:00:00 indicates the counters were cleared more than 231ms (and less than 232ms) ago.
Queueing strategy: fifo
First In, First Out queuing strategy (other queueing strategies you might see are priority-list, custom-list, and weighted fair).
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
Number of packets in output and input queues. Each number is followed by a slash, the maximum size of the queue, and the number of packets dropped due to a full queue.
5 minute input rate 4000 bits/sec, 2 packets/sec
5 minute output rate 1000 bits/sec, 1 packets/sec
Average number of bits and packets transmitted per second in the last 5 minutes. If the interface is not in promiscuous mode, it senses network traffic it sends and receives (rather than all network traffic).
The 5-minute input and output rates should be used only as an approximation of traffic per second during a given 5-minute period. These rates are exponentially weighted averages with a time constant of 5 minutes. A period of four time constants must pass before the average will be within two percent of the instantaneous rate of a uniform stream of traffic over that period.
Total number of error-free packets received by the system.
Total number of bytes, including data and MAC encapsulation, in the error free packets received by the system.
Received 1 broadcasts
Total number of broadcast or multicast packets received by the interface.
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.
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.
Number of times the receiver on the port was disabled, possibly due to buffer or processor overload.
Includes runts, giants, no buffer, CRC, frame, overrun, and ignored counts. Other input-related errors can also cause the input errors 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.
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.
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.
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.
Number of received packets ignored by the interface because the interface hardware ran low on internal buffers. These buffers are different than the system buffers mentioned previously in the buffer description. Broadcast storms and bursts of noise can cause the ignored count to be increased.
Number of times watchdog receive timer expired. It happens when receiving a packet with length greater than 2048.
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.
Total number of messages transmitted by the system.
Total number of bytes, including data and MAC encapsulation, transmitted by the system.
Number of times that the transmitter has been running faster than the router can handle. This may never be reported on some interfaces.
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.
Number of messages retransmitted due to an Ethernet collision. This is usually the result of an overextended LAN (Ethernet or transceiver cable too long, more than two repeaters between stations, or too many cascaded multiport transceivers). A packet that collides is counted only once in output packets.
Number of times an interface has been completely reset. This can happen if packets queued for transmission were not sent within several seconds. On a serial line, this can be caused by a malfunctioning modem that is not supplying the transmit clock signal, or by a cable problem. If the system notices that the carrier detect line of a serial interface is up, but the line protocol is down, it periodically resets the interface in an effort to restart it. Interface resets can also occur when an interface is looped back or shut down.
The transmit jabber timer expired.
Number of late collisions. Late collision happens when a collision occurs after transmitting the preamble.
Deferred indicates that the chip had to defer while ready to transmit a frame because the carrier was asserted.
Number of times the carrier was lost during transmission.
Number of times the carrier was not present during the transmission.
output buffer failures
Number of no resource errors received on the output.
output buffers swapped out
Number of packets swapped to DRAM.
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