show interfaces counters
Displays interface packet and byte counters for all interfaces or a specific interface, useful for monitoring traffic statistics and identifying errors or discards.
show interfaces countersWhen to Use This Command
- Check for excessive packet drops or errors on a specific interface to troubleshoot performance issues.
- Monitor traffic volume on an interface to verify bandwidth utilization or detect abnormal traffic patterns.
- Verify that interface counters are incrementing as expected after configuration changes or during testing.
- Compare input and output packet counts to identify asymmetric routing or unidirectional traffic.
Command Examples
Display counters for all interfaces
show interfaces countersInterface Input Packets Output Packets Input Bytes Output Bytes GigabitEthernet0/0 1234567 2345678 1234567890 2345678901 GigabitEthernet0/1 987654 876543 987654321 876543210 Serial0/0/0 12345 23456 12345678 23456789 Loopback0 0 0 0 0
The output shows each interface with its input/output packet and byte counters. 'Input Packets' counts packets received, 'Output Packets' counts packets sent. 'Input Bytes' and 'Output Bytes' are the total bytes. Use this to see traffic volume at a glance.
Display counters for a specific interface with errors
show interfaces counters GigabitEthernet0/0Interface Input Packets Output Packets Input Bytes Output Bytes GigabitEthernet0/0 1234567 2345678 1234567890 2345678901 5 minute input rate 1000 bits/sec, 2 packets/sec 5 minute output rate 2000 bits/sec, 3 packets/sec Input errors: 0, CRC errors: 0, Frame errors: 0, Overrun: 0, Ignored: 0 Output errors: 0, Collisions: 0, Interface resets: 0
For a specific interface, additional statistics are shown: 5-minute average input/output rates, and error counters. 'Input errors' include CRC, frame, overrun, ignored. 'Output errors' include collisions and interface resets. Zero errors indicate a healthy interface.
Understanding the Output
The 'show interfaces counters' command provides a summary of packet and byte counts for each interface. The main table has columns: Interface name, Input Packets, Output Packets, Input Bytes, Output Bytes. These counters are cumulative since the last reset (or router reload). When specifying a specific interface, additional lines show the 5-minute average input/output rates in bits/sec and packets/sec, followed by error counters. Input errors (CRC, frame, overrun, ignored) indicate physical layer or framing issues. Output errors (collisions, interface resets) suggest contention or hardware problems. High error counts or non-zero values typically indicate a problem that needs investigation. Compare input/output packet counts to verify bidirectional traffic; a large discrepancy may indicate a configuration issue or link asymmetry.
CCNA Exam Tips
CCNA exam may ask which command shows interface packet counts without detailed errors; 'show interfaces counters' is the answer.
Remember that 'show interfaces' includes errors and rates, while 'show interfaces counters' is a quick summary.
The exam might test that counters are cumulative and reset only on reload or with 'clear counters'.
Know that 'show interfaces counters' can be filtered by interface name to see specific interface statistics.
Common Mistakes
Confusing 'show interfaces counters' with 'show interfaces' which provides more detailed output including errors and rates.
Assuming counters reset automatically; they do not unless explicitly cleared with 'clear counters'.
Misinterpreting high input errors as a switch issue when it could be a cable or duplex mismatch problem.
Forgetting to specify an interface name when only interested in one interface, leading to unnecessary output.
Related Commands
clear counters
Resets interface counters (e.g., input/output errors, packets) to zero, typically used to clear statistics before monitoring or troubleshooting.
show interfaces
Displays detailed status and statistics for all interfaces or a specific interface, used to verify interface operational state, errors, and performance.
show interfaces status
Displays a summary of all switch interfaces including their status, VLAN, duplex, speed, and type, used to quickly verify interface connectivity and configuration.
Practice for the CCNA 200-301
Test your knowledge with hundreds of CCNA practice questions covering all exam domains.
Practice CCNA Questions