error :The frontend, protocol and port combination you entered matches another rule used by this load balancer. The frontend, protocol and port combination of each load balancing rule and inbound NAT rule on a load balancer must be unique.

@geetha b

Thank you for reaching out.

A load balancer rule is used to define how incoming traffic is distributed to all the instances within the backend pool. A load-balancing rule maps a given frontend IP configuration and port to multiple backend IP addresses and ports. The error above was received because a Load Balancer rule with the same frontend, protocol and port combination exists for your load balancer.

For example, I already have Load balancer Rule with the combination as shown below and I will get the same error as you got.

Now if I change the protocol to UDP. I will be able to add the Load Balancer Rule successfully.

If the aim here is to have Multiple frontends for Azure Load Balancer. Azure Load Balancer allows you to load balance services on multiple ports, multiple IP addresses, or both. You can use a public or internal load balancer to load balance traffic across a set of services like virtual machine scale sets or virtual machines (VMs).

This article describes the fundamentals of load balancing across multiple IP addresses using the same port and protocol.

Azure Load Balancer provides flexibility in defining the load balancing rules. A load balancing rule declares how an address and port on the frontend is mapped to the destination address and port on the backend. Whether or not backend ports are reused across rules depends on the type of the rule. Each type of rule has specific requirements that can affect host configuration and probe design. There are two types of rules:

1. The default rule with no backend port reuse.
2. The Floating IP rule where backend ports are reused.

Hope this helps!

Please share additional details regarding your set-up or the requirements if you have any questions. Thank you!