Load balancing configuration examples

Example HTTP load balancing to three real web servers

In this example, a virtual web server with IP address 192.168.37.4 on the Internet, is mapped to three real web servers connected to the FortiGate unit dmz1 interface. The real servers have IP addresses 10.10.123.42, 10.10.123.43, and 10.10.123.44. The virtual server uses the First Alive load balancing method. The configuration also includes an HTTP health check monitor that includes a URL used by the FortiGate unit for get requests to monitor the health of the real servers.

Connections to the virtual web server at IP address 192.168.37.4 from the Internet are translated and load balanced to the real servers by the FortiGate unit. First alive load balancing directs all sessions to the first real server. The computers on the Internet are unaware of this translation and load balancing and see a single virtual server at IP address 192.168.37.4 rather than the three real servers behind the FortiGate unit.

Virtual server configuration example

Web-based manager configuration

Use the following procedures to configure this load balancing setup from the web-based manager.

To add an HTTP health check monitor

In this example, the HTTP health check monitor includes the URL “/index.html” and the Matched Phrase “Fortinet products”.

1. Go to Policy & Objects > Health Check.
2. Select Create New.
3. Add an HTTP health check monitor that sends get requests to http://<real_server_IP_address>/index.html and searches the returned web page for the phrase “Fortinet products”.

Name	HTTP_health_chk_1
Type	HTTP
Port	80
URL	/index.html
Matched Content	Fortinet products
Interval	10 seconds
Timeout	2 seconds
Retry	3

4. Select OK.

To add the HTTP virtual server

1. Go to Policy & Objects > Virtual Servers.
2. Select Create New.
3. Add an HTTP virtual server that allows users on the Internet to connect to the real servers on the internal network. In this example, the FortiGate wan1 interface is connected to the Internet.

Name	Load_Bal_VS1
Type	HTTP
Interface	wan1
Virtual Server IP	192.168.37.4 The public IP address of the web server. The virtual server IP address is usually a static IP address obtained from your ISP for your web server. This address must be a unique IP address that is not used by another host and cannot be the same as the IP address of the external interface the virtual IP will be using. However, the external IP address must be routed to the selected interface. The virtual IP address and the external IP address can be on different subnets. When you add the virtual IP, the external interface responds to ARP requests for the external IP address.
Virtual Server Port	80
Load Balance Method	First Alive
Persistence	HTTP cookie
HTTP Multiplexing	Select. The FortiGate unit multiplexes multiple client into a few connections between the FortiGate unit and each real HTTP server. This can improve performance by reducing server overhead associated with establishing multiple connections.
Preserve Client IP	Select The FortiGate unit preserves the IP address of the client in the X-Forwarded-For HTTP header.
Health Check	Move the HTTP_health_chk_1 health check monitor to the Selected list.

4. Select OK.

To add the real servers and associate them with the virtual server

1. Go to Policy & Objects > Real Servers.
2. Select Create New.
3. Configure three real servers that include the virtual server Load_Bal_VS1. Each real server must include the IP address of a real server on the internal network.
   Configuration for the first real server.

Virtual Server	Load_Bal_VS1
IP Address	10.10.10.42
Port	80
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0 Setting Maximum Connections to 0 means the FortiGate unit does not limit the number of connections to the real server. Since the virtual server uses First Alive load balancing you may want to limit the number of connections to each real server to limit the traffic received by each server. In this example, the Maximum Connections is initially set to 0 but can be adjusted later if the real servers are getting too much traffic.

Configuration for the second real server.

Virtual Server	Load_Bal_VS1
IP Address	10.10.10.43
Port	80
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0 Setting Maximum Connections to 0 means the FortiGate unit does not limit the number of connections to the real server. Since the virtual server uses First Alive load balancing you may want to limit the number of connections to each real server to limit the traffic received by each server. In this example, the Maximum Connections is initially set to 0 but can be adjusted later if the real servers are getting too much traffic.

Configuration for the third real server.

Virtual Server	Load_Bal_VS1
IP Address	10.10.10.44
Port	80
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0 Setting Maximum Connections to 0 means the FortiGate unit does not limit the number of connections to the real server. Since the virtual server uses First Alive load balancing you may want to limit the number of connections to each real server to limit the traffic received by each server. In this example, the Maximum Connections is initially set to 0 but can be adjusted later if the real servers are getting too much traffic.

To add the virtual server to a security policy

Add a wan1 to dmz1 security policy that uses the virtual server so that when users on the Internet attempt to connect to the web server’s IP address, packets pass through the FortiGate unit from the wan1 interface to the dmz1 interface. The virtual IP translates the destination address of these packets from the virtual server IP address to the real server IP addresses.

1. Go to Policy & Objects > IPv4 Policy.
2. Select Create New.
3. Configure the security policy:

Policy Type	Firewall
Policy Subtype	Address
Incoming Interface	wan1
Source Address	all (or a more specific address)
Outgoing Interface	dmz1
Destination Address	Load_Bal_VS1
Schedule	always
Service	HTTP
Action	ACCEPT
Log Allowed Traffic	Select to log virtual server traffic
Enable NAT	Select this option and select Use Destination Interface Address.

4. Select other security policy options as required.
5. Select OK.

CLI configuration

Use the following procedure to configure this load balancing setup from the CLI.

To configure HTTP load balancing

1. Use the following command to add an HTTP health check monitor that sends get requests to http://<real_server_IP_address>/index.html and searches the returned web page for the phrase “Fortinet products”.

config firewall ldb-monitor

edit HTTP_health_chk_1

set type http

set port 80

set http-get /index.html

set http-match “Fortinet products”

set interval 10

set timeout 2

set retry 3

end

 

2. Use the following command to add an HTTP virtual server that allows users on the Internet to connect to the real servers on the internal network. In this example, the FortiGate wan1 interface is connected to the Internet.

config firewall vip

edit Load-Bal_VS1

set type server-load-balance

set server-type http

set ldb-method first-alive

set http-multiplex enable

set http-ip-header enable

set extip 192.168.37.4

set extintf wan1

set extport 80

set persistence http-cookie

set monitor HTTP_health_chk_1

config realservers

edit 1

set ip 10.10.10.42

set port 80

next

edit 2

set ip 10.10.10.43

set port 80

next

edit 3

set ip 10.10.10.44

set port 80

end

end

 

3. Use the following command to add a security policy that includes the load balance virtual server as the destination address.

config firewall policy

edit 0

set srcintf wan1

set srcaddr all

set dstintf dmz1

set dstaddr Load-Bal_VS1

set action accept

set schedule always

set service ALL

set nat enable

end

Configure other security policy settings as required.

Example Basic IP load balancing configuration

This example shows how to add a server load balancing virtual IP that load balances all traffic among 3 real servers. In the example the Internet is connected to port2 and the virtual IP address of the virtual server is 192.168.20.20. The load balancing method is weighted. The IP addresses of the real servers are 10.10.10.1, 10.10.10.2, and 10.10.10.3. The weights for the real servers are 1, 2, and 3. The default weight is 1 and does not have to be changed for the first real server.

config firewall vip

edit All_Load_Balance

set type server-load-balance

set server-type ip

set extintf port2

set extip 192.168.20.20

set ldb-method weighted

config realservers

edit 1

set ip 10.10.10.1

next

edit 2

set ip 10.10.10.2

set weight 2

next

edit 3

set ip 10.10.10.3

set weight 3

end

end

Example Adding a server load balance port forwarding virtual IP

In this example, a virtual web server with IP address 192.168.37.4 on the Internet, is mapped to three real web servers connected to the FortiGate unit dmz1 interface. The real servers have IP addresses 10.10.123.42, 10.10.123.43, and 10.10.123.44. The virtual server uses the First Alive load balancing method.

Each real server accepts HTTP connections on a different port number. The first real server accepts connections on port 8080, the second on port 8081, and the third on 8082. The configuration also includes an HTTP health check monitor that includes a URL used by the FortiGate unit for get requests to monitor the health of the real servers.

Connections to the virtual web server at IP address 192.168.37.4 from the Internet are translated and load balanced to the real servers by the FortiGate unit. First alive load balancing directs all sessions to the first real server. The computers on the Internet are unaware of this translation and load balancing and see a single virtual server at IP address 192.168.37.4 rather than the three real servers behind the FortiGate unit.

Server load balance virtual IP port forwarding

To complete this configuration, all of the steps would be the same as in Example HTTP load balancing to three real web servers except for configuring the real servers.

To add the real servers and associate them with the virtual server

Use the following steps to configure the FortiGate unit to port forward HTTP packets to the three real servers on ports 8080, 8081, and 8082.

1. Go to Policy & Objects > Real Servers.
2. Select Create New.
3. Configure three real servers that include the virtual server Load_Bal_VS1. Each real server must include the IP address of a real server on the internal network and have a different port number.
   
   Configuration for the first real server.

Virtual Server	Load_Bal_VS1
IP	10.10.10.42
Port	8080
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0

Configuration for the second real server.

Virtual Server	Load_Bal_VS1
IP	10.10.10.43
Port	8081
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0

Configuration for the third real server.

Virtual Server	Load_Bal_VS1
IP	10.10.10.44
Port	8082
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0

Example Weighted load balancing configuration

This example shows how to using firewall load balancing to load balances all traffic among 3 real servers. In the example the Internet is connected to port2 and the virtual IP address of the virtual server is 192.168.20.20. The load balancing method is weighted. The IP addresses of the real servers are 10.10.10.1, 10.10.10.2, and 10.10.10.3. The weights for the real servers are 1, 2, and 3.

This configuration does not include a health check monitor.

Web-based manager configuration

Use the following procedures to configure this load balancing setup from the web-based manager.

To add the HTTP virtual server

1. Go to Policy & Objects > Virtual Servers.
2. Select Create New.
3. Add an IP virtual server that allows users on the Internet to connect to the real servers on the internal network. In this example, the FortiGate port2 interface is connected to the Internet.

Name	HTTP_weghted_LB
Type	IP
Interface	port2
Virtual Server IP	192.168.20.20
Load Balance Method	Weighted

All other virtual server settings are not required or cannot be changed.

4. Select OK.

To add the real servers and associate them with the virtual server

1. Go to Policy & Objects > Real Servers.
2. Select Create New.
3. Configure three real servers that include the virtual server All_Load _Balance. Because the Load Balancing Method is Weighted, each real server includes a weight. Servers with a greater weight receive a greater proportion of forwarded connections,
   
   Configuration for the first real server.

Virtual Server	HTTP_weghted_LB
IP Address	10.10.10.1
Port	Cannot be configured because the virtual server is an IP server.
Weight	1
Maximum Connections	0 Setting Maximum Connections to 0 means the FortiGate unit does not limit the number of connections to the real server. Since the virtual server uses First Alive load balancing you may want to limit the number of connections to each real server to limit the traffic received by each server. In this example, the Maximum Connections is initially set to 0 but can be adjusted later if the real servers are getting too much traffic.

Configuration for the second real server.

Virtual Server	HTTP_weghted_LB
IP Address	10.10.10.2
Port	Cannot be configured because the virtual server is an IP server.
Weight	2
Maximum Connections	0 Setting Maximum Connections to 0 means the FortiGate unit does not limit the number of connections to the real server. Since the virtual server uses First Alive load balancing you may want to limit the number of connections to each real server to limit the traffic received by each server. In this example, the Maximum Connections is initially set to 0 but can be adjusted later if the real servers are getting too much traffic.

Configuration for the third real server.

Virtual Server	HTTP_weghted_LB
IP Address	10.10.10.3
Port	Cannot be configured because the virtual server is an IP server.
Weight	3
Maximum Connections	0 Setting Maximum Connections to 0 means the FortiGate unit does not limit the number of connections to the real server. Since the virtual server uses First Alive load balancing you may want to limit the number of connections to each real server to limit the traffic received by each server. In this example, the Maximum Connections is initially set to 0 but can be adjusted later if the real servers are getting too much traffic.

To add the virtual server to a security policy

Add a port2 to port1 security policy that uses the virtual server so that when users on the Internet attempt to connect to the web server’s IP address, packets pass through the FortiGate unit from the wan1 interface to the dmz1 interface. The virtual IP translates the destination address of these packets from the virtual server IP address to the real server IP addresses.

1. Go to Policy & Objects > IPv4 Policy.
2. Select Create New.
3. Configure the security policy:

Policy Type	Firewall
Policy Subtype	Address
Incoming Interface	port2
Source Address	all (or a more specific address)
Outgoing Interface	port1
Destination Address	HTTP_weghted_LB
Schedule	always
Service	ALL
Action	ACCEPT
Enable NAT	Select this option and select Use Destination Interface Address.

4. Select other security policy options as required.
5. Select OK.

CLI configuration

Load balancing is configured from the CLI using the config firewall vip command and by setting type to server-load-balance. The default weight is 1 and does not have to be changed for the first real server.

Use the following command to add the virtual server and the three weighted real servers.

config firewall vip

edit HTTP_weghted_LB

set type server-load-balance

set server-type ip

set extintf port2

set extip 192.168.20.20

set ldb-method weighted

config realservers

edit 1

set ip 10.10.10.1

next

edit 2

set ip 10.10.10.2

set weight 2

next

edit 3

set ip 10.10.10.3

set weight 3

end

end

Example HTTP and HTTPS persistence configuration

This example shows how to add a virtual server named HTTP_Load_Balance that load balances HTTP traffic using port 80 and a second virtual server named HTTPS_Load_Balance that load balances HTTPS traffic using port 443. The Internet is connected to port2 and the virtual IP address of the virtual server is 192.168.20.20. Both server load balancing virtual IPs load balance sessions to the same three real servers with IP addresses 10.10.10.2, 10.10.10.2, and 10.10.10.3. The real servers provide HTTP and HTTPS services.

For both virtual servers, persistence is set to HTTP Cookie to enable HTTP cookie persistence.

To add the HTTP and HTTPS virtual servers

1. Go to Policy & Objects > Virtual Servers.
2. Add the HTTP virtual server that includes HTTP Cookie persistence.

Name	HTTP_Load_Balance
Type	HTTP
Interface	port2
Virtual Server IP	192.168.20.20
Virtual Server Port	80 In this example the virtual server uses port 8080 for HTTP sessions instead of port 80.
Load Balance Method	Static
Persistence	HTTP cookie

3. Select OK.
4. Select Create New.
5. Add the HTTPs virtual server that also includes HTTP Cookie persistence.

Name	HTTPS_Load_Balance
Type	HTTPS
Interface	port2
Virtual Server IP	192.168.20.20
Virtual Server Port	443
Load Balance Method	Static
Persistence	HTTP cookie

6. Select OK.

To add the real servers and associate them with the virtual servers

1. Go to Policy & Objects > Real Servers.
2. Select Create New.
3. Configure three real servers for HTTP that include the virtual server HTTP_Load_Balance.
   
   Configuration for the first HTTP real server.

Virtual Server	HTTP_Load_Balance
IP Address	10.10.10.1
Port	80
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0

Configuration for the second HTTP real server.

Virtual Server	HTTP_Load_Balance
IP Address	10.10.10.2
Port	80
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0

Configuration for the third HTTP real server.

Virtual Server	HTTP_Load_Balance
IP Address	10.10.10.3
Port	80
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0

4. Configure three real servers for HTTPS that include the virtual server HTTPS_Load_Balance.
   
   Configuration for the first HTTPS real server.

Virtual Server	HTTP_Load_Balance
IP Address	10.10.10.1
Port	443
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0

Configuration for the second HTTPS real server.

Virtual Server	HTTP_Load_Balance
IP Address	10.10.10.2
Port	443
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0

Configuration for the third HTTPS real server.

Virtual Server	HTTPS_Load_Balance
IP Address	10.10.10.3
Port	443
Weight	Cannot be configured because the virtual server does not include weighted load balancing.
Maximum Connections	0

To add the virtual servers to security policies

Add a port2 to port1 security policy that uses the virtual server so that when users on the Internet attempt to connect to the web server’s IP address, packets pass through the FortiGate unit from the wan1 interface to the dmz1 interface. The virtual IP translates the destination address of these packets from the virtual server IP address to the real server IP addresses.

1. Go to Policy & Objects > IPv4 Policy.
2. Select Create New.
3. Configure the HTTP security policy:

Policy Type	Firewall
Policy Subtype	Address
Incoming Interface	port2
Source Address	all
Outgoing Interface	port1
Destination Address	HTTP_Load_Balance
Schedule	always
Service	HTTP
Action	ACCEPT
Enable NAT	Select this option and select Use Destination Interface Address.

4. Select other security policy options as required.
5. Select OK.
6. Select Create New.
7. Configure the HTTP security policy:

Policy Type	Firewall
Policy Subtype	Address
Incoming Interface	port2
Source Address	all
Outgoing Interface	port1
Destination Address	HTTPS_Load_Balance
Schedule	always
Service	HTTPS
Action	ACCEPT
Enable NAT	Select this option and select Use Destination Interface Address.

8. Select other security policy options as required.
9. Select OK.

CLI configuration: adding persistence for a specific domain

Load balancing is configured from the CLI using the config firewall vip command and by setting type to server-load-balance.

For the CLI configuration, both virtual servers include setting http-cookie-domain to .example.org because HTTP cookie persistence is just required for the example.org domain.

First, the configuration for the HTTP virtual IP:

config firewall vip

edit HTTP_Load_Balance

set type server-load-balance

set server-type http

set extport 8080

set extintf port2

set extip 192.168.20.20

set persistence http-cookie

set http-cookie-domain .example.org

config realservers

edit 1

set ip 10.10.10.1

next

edit 2

set ip 10.10.10.2

next

edit 3

set ip 10.10.10.3

end

end

Second, the configuration for the HTTPS virtual IP. In this configuration you don’t have to set extport to 443 because extport is automatically set to 443 when server-type is set to https.

config firewall vip

edit HTTPS_Load_Balance

set type server-load-balance

set server-type https

set extport 443

set extintf port2

set extip 192.168.20.20

set persistence http-cookie

set http-cookie-domain .example.org

config realservers

edit 1

set ip 10.10.10.1

next

edit 2

set ip 10.10.10.2

next

edit 3

set ip 10.10.10.3

end

end