Frequently asked questions

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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 dynamic verification 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, dynamic verification tests reachability only from the source to the forwarding VM.

The configuration analysis can produce multiple traces for a given test; how does dynamic verification handle such tests?

Dynamic verification does not provide a breakdown into multiple traces.

For context, the Connectivity Tests configuration analysis can show multiple trace routes in the following situations:

  • The destination IP address is a load balancer. In this case, there is a trace for each backend VM.
  • ECMP routing is being used. Each trace represents a 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, there would be a trace per source entity.

The first two scenarios in the preceding list—load balancing and ECMP—are not currently supported by dynamic verification. (Only direct VM-VM connectivity is supported.)

In the case of ambiguous source definitions, Connectivity Tests does not perform or report dynamic verification analysis.

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