> ## Documentation Index
> Fetch the complete documentation index at: https://checklyhq.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Network diagnostic tools

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.

## 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.

### How to access

<Note>
  TCP dumps are currently only available for API checks.
</Note>

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.

## 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

### How to access

<Note>
  Traceroute is currently only available for API checks.
</Note>

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.

## ICMP monitors

[ICMP monitors](/detect/uptime-monitoring/icmp-monitors/overview) 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](/detect/uptime-monitoring/icmp-monitors/overview) and [configuration](/detect/uptime-monitoring/icmp-monitors/configuration) docs.