The type of ActiveGate you need depends on the Dynatrace deployment model you're using, SaaS or Managed.
If you use Dynatrace SaaS, the only type of ActiveGate you need is the Environment ActiveGate. While technically an optional component, there are numerous benefits to installing an Environment ActiveGate.
A single Environment ActiveGate can manage up to 2,000 OneAgents. However, performance problems can arise at such high volume. If this happens, you should add at least one more Environment ActiveGate to your network. You don’t need to install all Environment ActiveGates initially—you can add additional Environment ActiveGates at any time. However, if you've set up several monitoring environments, it may be cumbersome to install and maintain multiple Environment ActiveGates. Therefore, Dynatrace enables you to configure a single ActiveGate in support of multiple monitoring environments. This significantly reduces maintenance and setup overhead. Thanks to this feature, you don't need to deploy multiple Environment ActiveGates and adjust firewall settings for each Environment ActiveGate installation. Such multi-environment ActiveGates are capable of handling all traffic from the environments they are associated with.
If you use Dynatrace Managed, you'll need both ActiveGate types. While technically an optional component, there are numerous benefits to installing an Environment ActiveGate.
An Environment ActiveGate can be installed for each of your monitoring environments if they are high-load, production-ready installations. However, an Environment ActiveGate is bound to a specific environment and is thus only capable of handling traffic from OneAgents that belong to the same environment as the ActiveGate.
Therefore, for Dynatrace Managed, you also need a Cluster ActiveGate, which can be used as a proxy between your Managed cluster and multiple environments.