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When troubleshooting network issues like dropped packets or broken TCP handshakes you often require low-level visibility into what’s happening on the network. That’s where network diagnostic tools come in. They help you understand how data moves through a network and where things might be breaking down. Checkly provides:
  • TCP dumps: capture network traffic to inspect packet-level behavior
  • Traceroute report: trace the path your request takes across the internet
  • ICMP monitors: continuously monitor host reachability, latency, and packet loss
Whether you’re debugging a slow response or tracing a connection failure, these tools can help you get to the root of the problem.

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TCP dumps

TCP dumps give you a detailed look at what’s happening at the packet level when a request fails. They capture the packets exchanged between Checkly and your target, letting you analyze things like:
  • Did the TCP handshake complete?
  • Was the TLS handshake successful?
  • Were packets dropped, delayed, or malformed?
This level of visibility is especially helpful for diagnosing flaky networking behavior.

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How to access

TCP dumps are currently only available for API checks.
For checks that fail due to network errors (e.g. DNS resolution issues, TCP handshake failures, connection timeouts), you’ll find a Download PCAP button in the Network Diagnostics section of the check results page. This gives you a .pcap file with the raw packet data from that request. You can open this file using tools like Wireshark to inspect each packet in detail.

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Traceroute report

Traceroute shows the path your request takes across the network and how each hop behaves. A report typically includes:
  • The sequence of network hops between Checkly and your target
  • Packet loss percentage per hop
  • Latency statistics (last, average, best, worst, standard deviation)
This makes it especially useful for diagnosing:
  • Where along the route packets are being dropped
  • Which hops introduce unusual latency or instability

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How to access

Traceroute is currently only available for API checks.
On checks that fail due to network errors (e.g. DNS resolution issues, TCP handshake failures, connection timeouts), a traceroute report is displayed in the Network Diagnostics section of the check results page. The table shows each hop, its IP or hostname, along with metrics such as packet loss, latency, and jitter.

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ICMP monitors

ICMP monitors let you proactively detect network issues by continuously pinging a host. They measure round-trip latency and packet loss over time, making them useful for:
  • Verifying reachability of hosts that don’t expose HTTP endpoints
  • Detecting network-level outages before they affect application-layer checks
  • Tracking latency and packet loss trends across regions
Learn more about setting up ICMP monitors in the ICMP monitor overview and configuration docs.