Verifying your cisco Router configuration with the Show Interface Command.
Verifying your cisco router configuration
available interfaces to configure. The only cisco router interfaces that are not logical are Ethernet and Serial.
Router#sh int ?
Ethernet IEEE 802.3
Null Null interface
Serial Serial
accounting Show interface accounting
crb Show interface routing/bridging information
irb Show interface routing/bridging information
<cr>
The next command is show interface ethernet 0 and shows us the hardware
address, logical address, and encapsulation method, as well as statistics
on collisions.
Router#sh int e0
Ethernet0 is up, line protocol is up
Hardware is Lance, address is 0010.7b7f.c26c (bia
0010.7b7f.c26c)
Internet address is 192.168.88.2/24
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set, keepalive set (10
sec)
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:08:23, output 00:08:20, output hang never
Last clearing of “show interface” counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
25 packets input, 2459 bytes, 0 no buffer
Received 25 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored,
0 abort
0 input packets with dribble condition detected
33 packets output, 7056 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets 0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out
The most important status of the show interface command is the output
of the line and data-link protocol status. If Ethernet 0 is up, line protocol
is up, and the line is up and running.
RouterA#sh int e0
The output will be the following
Ethernet0 is up, line protocol is up
The first parameter refers to the Physical layer and is up when it receives carrier
detect.
The second parameter refers to the Data Link layer and looks for keepalives from the connecting end.
verifying the cisco Serial Interface configuration
RouterA#sh int s0
Serial0 is up, line protocol is down
If you see the line is up, but the protocol is down, you are having a clocking
(keepalive) or framing issue. Check the keepalives on both ends to make
sure they match; the clock rate is set, if needed; and the encapsulation type
is the same on both ends.
RouterA#sh int s0
Serial0 is down, line protocol is down
If you see the line interface and protocol down, it is a cable or interface problem.
Also, if one end is administratively shut down, then the remote end
would show down and down. To turn on the interface, type the command no
shutdown in interface configuration.
RouterB#sh int s0
Serial0 is administratively down, line protocol is down
The next command demonstrates the serial line and the Maximum Transmission
Unit (MTU), which is 1500 bytes by default. It also shows the
default bandwidth (BW) on all Cisco serial links: 1.544Kbs. This is used to
determine the bandwidth of the line for routing protocols such as IGRP,
EIGRP, and OSPF. Another important configuration to notice is the keepalive,
which is 10 seconds by default. Each router sends a keepalive message
to its neighbor every 10 seconds.
If both routers are not configured for the same keepalive time, it will not work.
You can clear the counters on the interface by typing the command clear counters.
Router#sh int s0
Serial0 is up, line protocol is up
Hardware is HD64570
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation HDLC, loopback not set, keepalive set (10 sec)
Last input never, output never, output hang never
Last clearing of “show interface” counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 0 packets output, 0 bytes, 0 under runs
0 output errors, 0 collisions, 16 interface resets 0 output buffer failures, 0 output buffers swapped out 0 carrier transitions
DCD=down DSR=down DTR=down RTS=down CTS=down
Router#clear counters ?
Ethernet IEEE 802.3
Null Null interface
Serial Serial
<cr>
Router#clear counters s0
Clear “show interface” counters on this interface
[confirm]return
Router#