ping [ip]
The ping command sends ICMP echo requests to a destination IP address to test network connectivity and measure round-trip time.
ping [ip]When to Use This Command
- Verify reachability of a remote host after configuring a new network link
- Troubleshoot intermittent connectivity issues by observing packet loss patterns
- Check latency between two devices to assess network performance
- Confirm that a firewall or ACL is not blocking traffic by testing with extended ping options
Command Examples
Basic ping to a known host
ping 192.168.1.1Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
The output shows five exclamation marks indicating all five echo replies were received. The success rate is 100% with round-trip times: minimum 1 ms, average 2 ms, maximum 4 ms.
Ping with extended options (repeat count and size)
ping 10.0.0.1 repeat 10 size 1500Type escape sequence to abort. Sending 10, 1500-byte ICMP Echos to 10.0.0.1, timeout is 2 seconds: !!!!!!!!!! Success rate is 100 percent (10/10), round-trip min/avg/max = 10/12/15 ms
This sends 10 large packets (1500 bytes) to test jumbo frame support or stress the link. All ten replies received with slightly higher latency due to larger packet size.
Understanding the Output
The ping output begins with 'Type escape sequence to abort.' indicating you can press Ctrl+Shift+6 to stop. Then it shows the parameters: number of packets, size in bytes, destination IP, and timeout. Each '.' indicates a timeout (no reply), while '!' indicates a successful reply. 'U' means destination unreachable. The summary line shows success rate (percentage and fraction) and round-trip time statistics (min/avg/max). A 100% success rate with low and consistent RTT indicates good connectivity. Partial loss (e.g., 80%) suggests intermittent issues. High RTT or increasing RTT may indicate congestion or long paths. Watch for 'U' which often indicates a routing problem or ACL blocking.
CCNA Exam Tips
Know that '!' means success and '.' means timeout; exam may show output and ask you to interpret connectivity
Remember that ping uses ICMP, which may be blocked by security policies; a failed ping doesn't always mean no connectivity
Extended ping (from privileged EXEC) allows setting source interface, repeat count, size, and timeout; be ready to use it in troubleshooting scenarios
The round-trip time (RTT) is measured in milliseconds; high RTT or jitter can indicate network issues
Common Mistakes
Assuming a failed ping means the destination is down; ICMP may be blocked by ACLs or firewalls
Not using extended ping to specify a source interface when multiple paths exist, leading to misleading results
Interpreting a single '.' as a major failure; it could be due to transient congestion or ARP resolution delay
Related Commands
show interfaces
Displays detailed status and statistics for all interfaces or a specific interface, used to verify interface operational state, errors, and performance.
show ip route
Displays the current IP routing table on a Cisco router, used to verify routes, check next-hop addresses, and troubleshoot connectivity issues.
traceroute [ip]
Traces the route packets take from the source device to a destination IP address, showing each hop along the path, used to diagnose network path issues and latency.
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