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.