Restoring Application Delivery Through Azure Load Balancer

Table of Contents

1. Challenge

   Access the Azure portal and review the pre-provisioned environment

   • Log in to the Azure portal using the provided lab credentials and open Azure Cloud Shell.
   • Review the pre-provisioned environment, including the load balancer, backend pool, and backend virtual machines.
   • Identify the two network security policy layers that apply to inbound backend traffic.
2. Challenge

   Reproduce the failed application-delivery path

   • Attempt to reach the application through the load balancer frontend and observe the failure.
   • Confirm the current backend isolation state to establish a baseline.
3. Challenge

   Inspect load balancer health and the layered security policy

   • Review the load balancer health probe, load-balancing rule, and backend pool membership.
   • Check the backend pool health status reported by the load balancer.
   • Compare the centralized subnet policy against the effective rules on a backend network interface to identify the blocking condition.
4. Challenge

   Apply a narrowly scoped fix that preserves backend isolation

   • Permit the health probe from the load balancer service tag on the application port only.
   • Permit delivered application traffic on the application port only.
   • Confirm the catch-all deny rule remains in place so backend isolation is preserved.
5. Challenge

   Verify application delivery and backend isolation

   • Verify the application responds through the load balancer frontend and backend health recovers.
   • Verify that inbound management ports remain denied on the backend network interfaces.
   • Verify that the backend virtual machines still carry no public IP addresses.