Server Load Balancing

Server load balancing allows you to distribute traffic between multiple internal servers. It is commonly used with web servers and SMTP servers though it can be used for any service that uses TCP.

There are two portions of configuration for the server load balancer. Virtual server pools define the list of servers to be used, which port they listen on, and monitoring method to be used. Virtual servers define the IP address and port to listen on, and the appropriate pool to direct the incoming traffic to that IP address and port.

After the configuring Server Pools and Servers, you will need to create firewall rules to allow access to the servers in the pool. Firewall configuration is explained below.

To configure Virtual server pools:

1. Go to: Services --> Load Balancer --> Click + button to add a new pool.
2. Name --> Enter a name for the pool here. The name is referenced later when configuring virtual server.
3. Description --> You may enter an optional description here/
4. Type --> Select 'Server'
5. Behaviour --> Select 'Load Balancing'
6. Port --> This is the port your servers are listening on internally. This can be different from the external port.
7. Monitor --> Defines the type of monitoring to use. Selecting 'TCP' will make the balancer connect to the port defined above, if it cannot connect, server is considered down. Choosing 'ICMP' will monitor the defined servers by pinging them, and will be marked down if there is no ping response.
8. Monitor IP --> Not applicable with server load balancing
9. Server IP Address --> Fill in the IP address of the servers in the pool.
10. List --> Shows the list of servers you have added to this pool. You can remove a server from the pool by clicking on its IP address and clicking remove from pool.
11. Click on 'Save' and proceed to configure virtual servers.

To Configure virtual servers:

1. Name --> Enter a name for the virtual server here, this is not parsed.
2. Description --> You may enter a long description here, its not parsed.
3. IP Address --> Enter the IP address that the virtual server will listen on. This is usually your WAN IP or a Virtual IP on WAN interface.
4. Port --> This is the port the virtual server will listen on. It can be different from the port on your servers are listening internally.
5. Virtual Server Pool --> Select the previously configured pool from the list.

Firewall Rules:

Configure firewall rules to allow traffic to the server pool. Firewall rules must permit traffic to the internal private IP addresses of the servers and to the port they are listening on internally. Create an Alias for the servers in the pool, and using the Alias create a single firewall rule on the WAN (usually) interface where the traffic destined to the pool will be initiated allowing the appropriate source (usually Any) to destination of the Alias created for the pool.

Now that you have configured servers, pool and the firewall rule, the server load balancing setup should be up and running.