Understanding the 'show interface' Command on Cisco Devices

 Show Interface Command

The show interface command is a powerful diagnostic tool used primarily on Cisco network devices (like routers and switches) to display detailed information about the status and statistics of network interfaces.

Purpose of show interface

It helps network administrators:

• Monitor interface status (up/down)
• Check for errors or performance issues
• View traffic statistics
• Diagnose connectivity problems

Basic Syntax

1 show interface [interface-id]

2

interface-id is the name of the interface, such as GigabitEthernet0/1, FastEthernet0/0, or Serial0/0/0.

Example Output

1 Router# show interface GigabitEthernet0/1

2 GigabitEthernet0/1 is up, line protocol is up

3 Hardware is iGbE, address is 0012.7f8b.1c01 (bia 0012.7f8b.1c01)

4 MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,

5 reliability 255/255, txload 1/255, rxload 1/255

6 Encapsulation ARPA, loopback not set

7 Keepalive set (10 sec)

8 Full Duplex, 1000Mbps, media type is RJ45

9 output flow-control is XON, input flow-control is XON

10 ARP type: ARPA, ARP Timeout 04:00:00

11 Last input 00:00:01, output 00:00:02, output hang never

12 Last clearing of "show interface" counters never

13 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

14 Queueing strategy: fifo

15 5 minute input rate 1000 bits/sec, 2 packets/sec

16 5 minute output rate 2000 bits/sec, 3 packets/sec

17      123456 packets input, 987654 bytes

18       0 input errors, O CRC, Ø frame, O overrun, 0 ignored

19       234567 packets output, 1234567 bytes

20       0 output errors, O collisions, O interface resets

21

Key Fields Explained

Common Use Cases

• Troubleshooting: Identify errors, drops, or misconfigurations.
• Performance Monitoring: Check bandwidth usage and traffic rates.
• Hardware Checks: Verify cable connections and interface status.