Show Interfaces Command in Cisco IOS

The primary purpose of the show interfaces command is for displaying the equipped interfaces and their status. Here’s the information you can get about an interface from this command:

  • Interface type
  • Status
  • Speed and duplex
  • Encapsulation
  • Errors on the interface
  • The last time the interface flapped
  • The last time the error counters were reset
  • Utilization
  • IP address, subnet mask, and MAC address

Therefore, when troubleshooting, configuring, or maintaining your network, the appropriate uses for the show interfaces command are:

  • Determine if the interface is up and if the protocol is up.
  • Determine if the interface has errors on it, especially CRC errors.
  • Find out the speed and duplex of the interface (if it’s Ethernet).
  • Learn the current utilization and utilization over the last five minutes.
  • Determine the last time an interface flapped.

First, lets look at some example output (this has been shortened):

cell_pe1#show interfaces
Ethernet0/0 is up, line protocol is up
Hardware is AmdP2, address is 0030.9432.93e0 (bia 0030.9432.93e0)
Description: Management LAN Interface – do not change!
Internet address is 192.168.1.209/24
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 00:00:02, output 00:00:02, output hang never
Last clearing of “show interface” counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
1169 packets input, 128452 bytes, 0 no buffer
Received 1169 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
2832 packets output, 347735 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out

From this output, you can see that the show interfaces command generates a lot of valuable information. However, when you have many interfaces on a router, the output begins to get cumbersome. Let’s look at how you can limit this output to get the information you need the most.

show interfaces {type of interface} {interface number}

You can also view of a summary of the output from the show interfaces command. Using this option, you can get a summary of all interfaces and statistics about each one. Here’s an example:

cell_pe1#show interfaces summary

*: interface is up
IHQ: pkts in input hold queue IQD: pkts dropped from input queue
OHQ: pkts in output hold queue OQD: pkts dropped from output queue
RXBS: rx rate (bits/sec) RXPS: rx rate (pkts/sec)
TXBS: tx rate (bits/sec) TXPS: tx rate (pkts/sec)
TRTL: throttle count

Interface IHQ IQD OHQ OQD RXBS RXPS TXBS TXPS TRTL
————————————————————————
* Ethernet0/0 0 0 0 0 0 0 0 0 0
* Serial0/0 0 0 0 0 0 0 0 0 0
Serial0/1 0 0 0 0 0 0 0 0 0
* Serial0/2 0 0 0 0 0 0 0 0 0
Serial0/3 0 0 0 0 0 0 0 0 0
* Loopback0 0 0 0 0 0 0 0 0 0

NOTE: No separate counters are maintained for subinterfaces
, hence Details of subinterface are not shown

You can also use this command with the pipe command [|] and the begin,include, or exclude options. Here’s an example of using include:

cell_pe1#show interfaces | inc Serial
Serial0/0 is up, line protocol is up
Hardware is PowerQUICC Serial
Serial0/1 is down, line protocol is down
Hardware is PowerQUICC Serial
Serial0/2 is up, line protocol is up
Hardware is PowerQUICC Serial
Serial0/3 is administratively down, line protocol is down
Hardware is PowerQUICC Serial

You can use begin to start the output on a line that contains a specific text string. This way, you can skip to a specific point in the output rather than looking through all of it.

cell_pe1#show interfaces | beg Serial
Serial0/0 is up, line protocol is up
Hardware is PowerQUICC Serial
Description: Interface to P1
Internet address is 136.0.0.1/16
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation HDLC, loopback not set…………..output omitted

We hope this helps you with using the show interfaces command.

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