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This document covers commonly asked questions about Connectivity Tests.
Does Connectivity Tests send a trace packet through my VPC network?
Yes, it does (for supported configurations). The live data plane analysis
feature tests connectivity by sending multiple trace packets from the source
endpoint to the destination. For details, see the following pages:
Can I test a configuration where I enabled the forwarding functions of my VM instance?
No. The configuration analysis traces a packet based on the configuration of
resources in your Google Cloud projects. For virtual machine (VM) instances
that use a customized image, Connectivity Tests doesn't have access to
the forwarding or routing configurations. However, Connectivity Tests
is still helpful in such cases because you can trace connectivity issues to your
Cloud NAT gateway VM, for example. Some examples of this type of configuration
are a VM acting as a Cloud NAT gateway, or a VM acting as a third-party
firewall, such as the Palo Alto Networks VM series. Similarly, live data plane
analysis tests reachability only from the source to the forwarding VM.
Why Connectivity Tests produces multiple traces for a given test?
The Connectivity Tests configuration analysis can show multiple traces
in the following situations:
ECMP routing is being used. In this case, Connectivity Tests
configuration analysis shows a trace for each possible route.
The source endpoint has an ambiguous definition. For example, a project
can have multiple entities with the same IP address, in different Virtual Private Cloud
networks. In this case, Connectivity Tests configuration analysis
shows a trace for each source entity.
Live data plane analysis doesn't provide a breakdown into multiple traces.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-28 UTC."],[],[],null,["# Frequently asked questions\n\nThis document covers commonly asked questions about Connectivity Tests.\n\nDoes Connectivity Tests send a trace packet through my VPC network?\n-------------------------------------------------------------------\n\nYes, it does (for supported configurations). The live data plane analysis\nfeature tests connectivity by sending multiple trace packets from the source\nendpoint to the destination. For details, see the following pages:\n\n- [What is reachability?](/network-intelligence-center/docs/connectivity-tests/concepts/overview#what-is-reachability)\n\n- [How Connectivity Tests works](/network-intelligence-center/docs/connectivity-tests/concepts/overview#how-it-works)\n\n- [Supported configurations (live data plane analysis)](/network-intelligence-center/docs/connectivity-tests/concepts/overview#supported-dynamic-configs)\n\nCan I test a configuration where I enabled the forwarding functions of my VM instance?\n--------------------------------------------------------------------------------------\n\nNo. The configuration analysis traces a packet based on the configuration of\nresources in your Google Cloud projects. For virtual machine (VM) instances\nthat use a customized image, Connectivity Tests doesn't have access to\nthe forwarding or routing configurations. However, Connectivity Tests\nis still helpful in such cases because you can trace connectivity issues to your\nCloud NAT gateway VM, for example. Some examples of this type of configuration\nare a VM acting as a Cloud NAT gateway, or a VM acting as a third-party\nfirewall, such as the Palo Alto Networks VM series. Similarly, live data plane\nanalysis tests reachability only from the source to the forwarding VM.\n\nWhy Connectivity Tests produces multiple traces for a given test?\n-----------------------------------------------------------------\n\nThe Connectivity Tests configuration analysis can show multiple traces\nin the following situations:\n\n- The destination is a load balancer. For more information, see [Number of traces in a test to a load balancer](/network-intelligence-center/docs/connectivity-tests/concepts/test-load-balancers#number-of-traces).\n- ECMP routing is being used. In this case, Connectivity Tests configuration analysis shows a trace for each possible route.\n- The source endpoint has an ambiguous definition. For example, a project can have multiple entities with the same IP address, in different Virtual Private Cloud networks. In this case, Connectivity Tests configuration analysis shows a trace for each source entity.\n\nLive data plane analysis doesn't provide a breakdown into multiple traces.\n\nWhat's next\n-----------\n\n- [Learn about Connectivity Tests](/network-intelligence-center/docs/connectivity-tests/concepts/overview)\n- [Troubleshoot Connectivity Tests](/network-intelligence-center/docs/connectivity-tests/support/troubleshooting)"]]
