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Testing Tunnel Performance with ping

Once your TUN-over-UDP tunnel is up and running, a simple and effective way to test connectivity and measure performance is by using the ping command.

In this setup, the TUN interfaces are configured as follows:

  • Client-side TUN device: tun0, IP: 10.0.0.1
  • Server-side TUN device: tun1, IP: 10.0.0.2

The tunnel allows bidirectional communication, so 10.0.0.1 should be able to successfully ping 10.0.0.2.

What Does ping Measure?​

ping sends ICMP Echo Request packets to a target IP address and waits for an Echo Reply. The main metric it reports is RTT (Round-Trip Time)—the time it takes for a packet to travel to the destination and back.

This makes ping a quick way to:

  • Verify that the tunnel is up and functional
  • Measure latency between endpoints
  • Spot signs of packet loss or jitter

Basic Usage​

From the device with IP 10.0.0.1, run:

ping 10.0.0.2

Sample output:

PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=1.42 ms
64 bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=1.39 ms
64 bytes from 10.0.0.2: icmp_seq=3 ttl=64 time=1.36 ms
^C
--- 10.0.0.2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 1.360/1.390/1.420/0.025 ms
  • time=X ms: This is the RTT for each packet.
  • min/avg/max/mdev: Summary statistics over the ping session.

Testing with Custom Intervals​

By default, ping sends one packet per second. You can adjust the interval using the -i option.

Example: High-Frequency Ping (every 0.2s)​

ping -i 0.2 10.0.0.2

This sends 5 packets per second, giving you more granular data.

You may need superuser privileges to use intervals below 0.2s.

Example: Low-Frequency Ping (every 5s)​

ping -i 5 10.0.0.2

Useful for long-term monitoring without generating much traffic.

Interpreting RTT​

  • Low and stable RTT indicates good tunnel performance.
  • High RTT may signal congestion, buffering, or distance.
  • Variable RTT (jitter) can cause issues for latency-sensitive applications.
  • Packet loss (reported at the end of the ping session) suggests network instability or configuration issues.

Stopping the Test​

Press Ctrl + C to stop the test and see summary statistics.

Summary​

Use ping to quickly verify tunnel functionality and get a feel for network performance. For deeper analysis, you can combine it with tools like iperf, tcpdump, or NanoPing’s own metrics/KPIs.

Let me know if you’d like a follow-up guide using iperf or scripting ping tests for automation.