Earlier in this chapter, we mentioned that you can control the incoming traffic by mapping a public port on the load balancer to a port on the backend address pool.
Such a way of control can be done with the load balancing rules.
Before adding any load balancing rules, ensure that you already have one backend pool and one probe for the same load balancer you want to add a rule to.
To do so, you need to follow these steps:
- Navigate to the load balancer; under SETTINGS, click on Load balancing rules, and a new blade will be opened, as shown in the following screenshot:
Figure 6.16: Load balancing rules
- To add a rule, click on Add, and a new blade will be opened, asking you to specify the following:
- Name: Specify a descriptive name for the rule.
- IP Version: Specify the IP version for which this rule will be applied.
- Frontend IP address: Specify the frontend IP address through which the clients will communicate with this load balancer on the selected IP address, and the service will have their traffic routed to the target VM using this rule.
- Protocol: Specify the protocol that will be used by this rule.
- Port: Specify the port through which the client will come on the load balancer.
- Backend port: Specify the port opened for this service on the VM. It might be similar to the frontend port, or it might be different.
- Backend pool: The virtual machines in the selected backend pool will be the target for the load-balanced traffic of this rule.
- Health probe: The probe that will be used by this rule to determine which virtual machines in the backend pool are healthy and can receive load-balanced traffic.
- Session persistence: As long as the session between the client and one of the backend pool VMs is open, it will redirect all of the incoming requests from the client to the same backend VM. You can specify the following options for this setting:
- None: This option will not enable the session's persistence
- Client IP: This option will enable the session's persistence and will redirect any requests coming from the same client IP to the the same backend VM
- Client IP and protocol: This option will enable session persistence and will redirect any requests coming from the same client IP and the same used protocol to the same backend VM
- Idle timeout: The period within which the TCP/HTTP connection will be opened without any active communication from the client.
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- Floating IP (direct server return): It is recommended to enable this feature only when configuring an SQL AlwaysOn Availability Group Listener. It can be enabled only when creating a rule, and if the port and backend port match:
Figure 6.17: Add a load balancing rule
- Once you have clicked on OK, the rule will be added within a couple of minutes.