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> Chapter 15 - High Availability > Virtual clusters > Virtual clustering overview

Virtual clustering overview

Virtual clustering is an extension of the FGCP for a cluster of two FortiGates operating with multiple VDOMS enabled. Virtual clustering operates in active-passive mode to provide failover protection between two instances of a VDOM operating on two different cluster units. You can also operate virtual clustering in active-active mode to use HA load balancing to load balance sessions between cluster units. Alternatively, by distributing VDOM processing between the two cluster units you can also configure virtual clustering to provide load balancing by distributing sessions for different VDOMs to each cluster unit.

The figure below shows an example virtual cluster configuration consisting of two FortiGates. The virtual cluster has two virtual domains, root and Eng_vdm.

The root virtual domain includes the port1 and port2 interfaces. The Eng_vdm virtual domain includes the port5 and port6 interfaces. The port3 and port4 interfaces (not shown in the diagram) are the HA heartbeat interfaces.

note icon This chapter describes setting up FortiGate virtual clustering with a cluster of two FortiGates with multiple VDOMs enabled. You can also create a cluster of three or four FortiGates operating with multiple VDOMS. A future version of this guide will include a configuration example of this setup.

Virtual clustering and failover protection

Virtual clustering operates on a cluster of two FortiGates with VDOMs enabled. Each VDOM creates a cluster between instances of the VDOMs on the two FortiGates in the virtual cluster. All traffic to and from the VDOM stays within the VDOM and is processed by the VDOM. One cluster unit is the primary unit for each VDOM and one cluster unit is the subordinate unit for each VDOM. The primary unit processes all traffic for the VDOM. The subordinate unit does not process traffic for the VDOM. If a cluster unit fails, all traffic fails over to the cluster unit that is still operating.

Virtual clustering and heartbeat interfaces

The HA heartbeat provides the same HA services in a virtual clustering configuration as in a standard HA configuration. One set of HA heartbeat interfaces provides HA heartbeat services for all of the VDOMs in the cluster. You do not have to add a heartbeat interface for each VDOM.

Example virtual cluster

Virtual clustering and HA override

For a virtual cluster configuration, override is enabled by default for both virtual clusters when you:

  • Enable VDOM partitioning from the GUI by moving virtual domains to virtual cluster 2
  • Enter set vcluster2 enable from the CLI config system ha command to enable virtual cluster 2.

Usually you would enable virtual cluster 2 and expect one cluster unit to be the primary unit for virtual cluster 1 and the other cluster unit to be the primary unit for virtual cluster 2. For this distribution to occur override must be enabled for both virtual clusters. Otherwise you will need to restart the cluster to force it to renegotiate.

note icon If override is enabled the cluster may renegotiate too often. You can choose to disable override at any time. If you decide to disable override, for best results, you should disable it for both cluster units.

For more information about HA override see HA override.

Virtual clustering and load balancing or VDOM partitioning

There are two ways to configure load balancing for virtual clustering. The first is to set the HA mode to active-active. The second is to configure VDOM partitioning. For virtual clustering, setting the HA Mode to active-active has the same result as active-active HA for a cluster without virtual domains. The primary unit receives all sessions and load balances them among the cluster units according to the load balancing schedule. All cluster units process traffic for all virtual domains.

In a VDOM partitioning virtual clustering configuration, the HA mode is set to active-passive. Even though virtual clustering operates in active-passive mode you can configure a form of load balancing by using VDOM partitioning to distribute traffic between both cluster units. To configure VDOM partitioning you set one cluster unit as the primary unit for some virtual domains and you set the other cluster unit as the primary unit for other virtual domains. All traffic for a virtual domain is processed by the primary unit for that virtual domain. You can control the distribution of traffic between the cluster units by adjusting which cluster unit is the primary unit for each virtual domain.

For example, you could have 4 VDOMs, two of which have a high traffic volume and two of which have a low traffic volume. You can configure each cluster unit to be the primary unit for one of the high volume VDOMs and one of the low volume VDOMs. As a result each cluster unit will be processing traffic for a high volume VDOM and a low volume VDOM, resulting in an even distribution of traffic between the cluster units. You can adjust the distribution at any time. For example, if a low volume VDOM becomes a high volume VDOM you can move it from one cluster unit to another until the best balance is achieved.

From the GUI you configure VDOM partitioning by setting the HA mode to active-passive and distributing virtual domains between Virtual Cluster 1 and Virtual Cluster 2. You can also configure different device priorities, port monitoring, and remote link failover, for Virtual Cluster 1 and Virtual Cluster 2.

note icon The device priorities for virtual cluster 1 and virtual cluster 2 are not synchronized between the FortiGates in the virtual cluster. You must configure these device priorities separately for each cluster unit.

From the CLI you configure VDOM partitioning by setting the HA mode to a-p. Then you configure device priority, port monitoring, and remote link failover and specify the VDOMs to include in virtual cluster 1 (vcluster 1). You do the same for virtual cluster 2 (vcluster 2) by entering the config secondary-vcluster command.

caution icon If your cluster has a VLAN that is part of a different VDOM than the phsyical interface that the VLAN has been added to, then you must configure VDOM partioning to keep both of these VDOMs in the same vitrual cluster (vcluster).

Failover protection does not change. If one cluster unit fails, all sessions are processed by the remaining cluster unit. No traffic interruption occurs for the virtual domains for which the still functioning cluster unit was the primary unit. Traffic may be interrupted temporarily for virtual domains for which the failed unit was the primary unit while processing fails over to the still functioning cluster unit.

If the failed cluster unit restarts and rejoins the virtual cluster, VDOM partitioning load balancing is restored.