You have an on-premises datacenter in Seattle and an Azure subscription that contains a Network Watcher resource in West US 2. You must document latency between your datacenter and West US 2 and between your datacenter and the East US 2 public Azure region while minimizing administrative effort. What should you do first?

To document latency between your on-premises datacenter and Azure regions, you need to use Connection Monitor. The first step is to create a Connection Monitor resource. Since your existing Network Watcher is in West US 2, and you want to monitor connections from your on-premises datacenter to West US 2 and East US 2, you should create the Connection Monitor resource within the West US 2 region. This allows it to leverage the existing Network Watcher and monitor connectivity to both specified Azure regions. Running Get-AzNetworkWatcherConnectionMonitor or Get-AzNetworkWatcherReachabilityProvidersList without an existing Connection Monitor would not provide the necessary data. Creating a Network Watcher in East US 2 is not required for monitoring from your on-premises datacenter to East US 2, as the Connection Monitor in West US 2 can handle this.