Port 5557 is a TCP port used by Azure Databricks for communication between the Databricks control plane (API) and the Databricks data plane (compute clusters). Here’s what you need to know:

Purpose:

• Inbound Communication: Azure Databricks uses port 5557 to establish inbound connections to your Databricks clusters. This is necessary for the control plane to manage and communicate with the compute resources in your workspace.
• Security: By default, Azure Databricks restricts inbound traffic on port 5557 to originate only from the Databricks service using service tags. This helps to ensure that only authorized Databricks components can access your clusters.

Network Security Group (NSG) Rules:

If you use Azure Databricks with VNET injection, you must configure your network security group (NSG) to allow inbound traffic on port 5557 from the AzureDatabricks service tag.

Secure Cluster Connectivity (SCC):

Azure Databricks offers a Secure Cluster Connectivity (SCC) feature that eliminates the need for inbound connections on port 5557. With SCC enabled, all communication between the control and data planes is outbound, simplifying network configuration and potentially improving security.

Additional Considerations:

• Custom Routing: If you have custom routing requirements, be careful when handling inbound traffic on port 5557, as improper routing could disrupt communication with your Databricks clusters.
• Monitoring: Monitor traffic on port 5557 to detect any unauthorized access attempts or anomalies.