To create an inbound NAT rule, you need to specify a frontend IP address and a frontend port for the load balancer to receive the traffic, and a backend IP address and a backend port for the load balancer to forward the traffic to1. According to the first table, LB1 has only one frontend IP address, which is
40.121.183.105. However, this frontend IP address is already used by the existing inbound NAT rule named rule1, which forwards port 80 to VM1 on port 802. Therefore, you cannot use the same frontend IP address and port for another inbound NAT rule.
To solve this problem, you need to create a new frontend IP address for LB1 before you can create the new inbound NAT rules. You can do this by using the Azure portal, PowerShell, or CLI3. After you create a new frontend IP address, you can use it to create the new inbound NAT rules that meet your requirements.