The ping Command
"Is the server up?" - Ping is your first diagnostic tool.
Basic Ping
Terminal
$ping google.com
PING google.com (142.250.185.78): 56 data bytes
64 bytes from 142.250.185.78: icmp_seq=0 ttl=117 time=14.2 ms
64 bytes from 142.250.185.78: icmp_seq=1 ttl=117 time=13.8 ms
^C
--- google.com ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1002ms
Press Ctrl+C to stop.
Understanding the Output
| Field | Meaning |
|---|---|
64 bytes | Response size |
icmp_seq | Packet sequence number |
ttl | Time To Live (hops remaining) |
time | Round-trip time (latency) |
packet loss | Percentage lost |
What's Good Latency?
- Under 50ms: Excellent
- 50-100ms: Good
- 100-200ms: Okay
- Over 200ms: Slow
Depends on distance. Same datacenter: under 1ms. Across continents: 100-200ms.
Limited Ping Count
Terminal
$ping -c 4 google.com
(sends 4 packets then stops)
-c 4 = count of 4 packets. No need to Ctrl+C.
Ping an IP Directly
Terminal
$ping -c 3 8.8.8.8
PING 8.8.8.8 (8.8.8.8): 56 data bytes
64 bytes from 8.8.8.8: icmp_seq=0 ttl=118 time=12.1 ms
...
This bypasses DNS. Useful for diagnosing: is it network or DNS?
Diagnosing Issues
No Response
Terminal
$ping -c 3 10.0.0.99
PING 10.0.0.99 (10.0.0.99): 56 data bytes
--- 10.0.0.99 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss
100% loss means: host is down, unreachable, or blocking ICMP.
High Latency
Terminal
$ping -c 3 server
64 bytes: icmp_seq=0 ttl=64 time=450.2 ms
64 bytes: icmp_seq=1 ttl=64 time=523.1 ms
Consistently high latency = network congestion or distant server.
Packet Loss
Terminal
$ping -c 10 server
10 packets transmitted, 7 received, 30% packet loss
30% loss = network problems. Investigate the path.
Quick Network Check
Terminal
$# Can I reach the internet?
$ping -c 2 8.8.8.8
$
$# Is DNS working?
$ping -c 2 google.com
$
$# Can I reach my gateway?
$ping -c 2 $(ip route | grep default | awk '{print $3}')
Troubleshooting Order
- Ping gateway (local network)
- Ping 8.8.8.8 (internet, skip DNS)
- Ping google.com (DNS + internet)
If 1 fails: local network issue. If 2 fails but 1 works: routing/firewall issue. If 3 fails but 2 works: DNS issue.
Knowledge Check
You can ping 8.8.8.8 but not google.com. What's the likely problem?
Quick Reference
| Command | Purpose |
|---|---|
ping host | Continuous ping (Ctrl+C to stop) |
ping -c 4 host | Send 4 packets |
ping 8.8.8.8 | Test internet (skip DNS) |
ping gateway | Test local network |
Key Takeaways
pingtests if a host is reachable- Use
-c Nfor limited packet count - Check latency (time) and packet loss
- Ping IP directly to bypass DNS
- 100% loss = down or blocking ICMP
Next: DNS troubleshooting.