Finding out an issue in network connectivity and performance in the cloud was a critical issue in the past due to the complex network of systems. The Azure Network Watcherhas addressed the problem and presented the solution in the form of check network connectivity. Basically, the feature is used to reduce the time of the problem detection and points out the basic issue in the infrastructure. No matter the issue is happened due to the potential user configuration or a platform, check network connectivity provides a valuable insight. It’s only accessible from PowerShell, Azure portal, REST API, and Azure CLI.
The Check Network Connectivity supports the following scenarios:
- VM to VM
- External endpoint to VM
- VM to an on-premise endpoint.
The below-mentioned picture shows how you can resolve network reachability issue by using network topology and Azure portal. It illustrates the connectivity of a VNet hosting, four subnets, and a multi-tier web application. Out of the four subnet, one is the database subnet and the other is the application subnet.
Click on the connectivity check which is present under Network Diagnostic Tools on the Azure portal. It also gives you the liberty to specify the source and destination of the VM and this specification are necessary to check to ensure the connectivity.
Once you complete the process, you get the detailed report of the reachable or unreachable statuses. It also informs you about the number of hops and latency required to reach the destination.
Here is an example of the connectivity check for the VM running the application tier to the VM running the database tier and it’s showing the status unreachable. The red color of the hop is the indication of an unreachable database and on clicking on the hop, you see the issue that is NSG rule blocking the traffic.
On rectifying the NSG rule, you can see an end-to-end connectivity and latency between source and destination. IP address, ARM URI, and FQDN are the destinations of the for connectivity check.