Troubleshooting Commands
195
Let's look at sample outputs from an Ethernet and Serial interface. After
each sample, we will go through a detailed explanation.
Router_A#show interface Ethernet 5/4
Ethernet5/4 is up, line protocol is up
Hardware is cxBus Ethernet, address is 009a.822e.51b6
(bia 90.323f.acdb)
Description: Connection to Router_B
Internet address is 172.16.1.1/24
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 255/
255, load 33/255
Encapsulation ARPA, loopback not set, keepalive set (10
sec)
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 101553 drops; input queue 0/75, 1327
drops
5 minute input rate 247000 bits/sec, 196 packets/sec
5 minute output rate 1329000 bits/sec, 333 packets/sec
421895792 packets input, 2524672293 bytes, 1 no
buffer
Received 453382 broadcasts, 0 runts, 0 giants
6 input errors, 1 CRC, 5 frame, 0 overrun, 494
ignored, 0 abort
0 input packets with dribble condition detected
618578101 packets output, 977287695 bytes, 0
underruns
0 output errors, 30979588 collisions, 1 interface
resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffers copied, 0 interrupts, 0 failures
Router_A#
The output starts with the most pertinent information--the physical
interface and line protocol status. In this case, both are up. There is much
argument as to what constitutes an "up" interface. It is very simple--the
controller sends a signal that there are electrons flowing through the physical
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