The CommuniGate Pro Dynamic Cluster can be used to control software load balancers (such as Linux IPVS), running on the same systems as the Cluster members. Select the cluster members to distribute the incoming traffic to. In a frontend-backend configuration, you would usually use all or some of the frontend servers for that.
Make sure that all selected cluster members have the VIP addresses configured as "loopback aliases" (see above).
Use the WebAdmin Interface to open the Cluster page in the Settings realm and select the Load Balancer group A for all selected servers:
Balancer Weight: Use this setting to specify relative weight of this server in the Load Balancer Group. The more this value, the larger part of incoming TCP connections and UDP packets will be directed to this server.
All or some of the selected servers should be equipped with a software load balancer, and they should have an "External Load Balancer" Helper application configured. This application should implement the Load Balancer Helper Protocol.
As soon as the first Load Balancer helper application starts on some Cluster Member, the Cluster Controller activates that Helper, making it direct all incoming traffic to its Cluster member, and distribute that traffic to all active Cluster members in its Load Balancer Group.
If the Cluster Member running the active Load Balancer fails or it is switched into the "non-ready" state, the Cluster Controller activates some other Load Balancer member in that group (if it can find one).
The CommuniGate Pro Linux package includes the Services/IPVSHelper.sh shell application that can be used to control the IPVS software load balancer.
The application expects that the VIP addresses are stored in the /etc/sysconfig/vipaddrs file, and the local interface (lo) aliases for these addresses have beeen created (see above).
Specify $Services/IPVSHelper.sh parameters as the External Load Balancer "program path", and start it by selecting the Helper checkbox. The following parameters are supported:
-p number: persistence: all connections from the same IP address will be directed to the same Cluster Member if they come within number seconds after the existing connection. Specify 0 (zero) to switch persistance off. The default value is 15 seconds.
-i interface: the ethernet interface used to receive packets addressed to the VIP address(es). The default value is eth0
-s number: the "syncID" value used to synchronize connection tables on the active load balancer and other Cluster Members that can become load balancers.