Configuring a high availability (HA) FortiWeb cluster

By default, FortiWeb appliances are each a single, standalone appliance. They operate independently.

If you have purchased more than one, however, you can configure the FortiWeb appliances to form an active-passive or active-active high availability (HA) FortiWeb cluster. This improves availability so that you can achieve 99.999% service level agreement (SLA) uptimes regardless of, for example, hardware failure or maintenance periods.

If you have multiple FortiWeb appliances but do not need failover, you can still synchronize the configuration. This can be useful for cloned network environments and externally load-balanced active-active HA. See Configuring a high availability (HA) FortiWeb cluster.

You can use the FortiWeb WCCP feature to create an active-active HA cluster. You synchronize the cluster members using FortiWeb's configuration synchronization feature so that each cluster member is ready to act as backup if the other appliance is not available. The WCCP server provides load balancing between the HA pair and redirects all traffic to one cluster member if the other member is unavailable. For more information, see Example: Using WCCP with multiple FortiWeb appliances.

HA requirements

For active-passive HA, you need two identical physical FortiWeb appliances; for active-active HA, you need two or more (up to eight) identical physical FortiWeb appliances. (i.e., the same hardware model and firmware version (for example, both appliances could be a FortiWeb 3000C running FortiWeb 5.3.4))
Redundant network topology: if the active or master appliance fails, physical network cabling and routes must be able to redirect web traffic to the standby or slave appliances (see Topologies for high availability (HA) clustering)
At least one physical port on each HA appliance connected directly, via crossover cables, or through switches (see HA heartbeat & synchronization)
For FortiWeb-VM:
- A valid license for all cluster members. You cannot configure HA with trial licences.
- Configure the vNetwork interfaces that carry heartbeat and synchronization traffic to operate in promiscuous mode and accept MAC address changes.
- Ensure the cluster members have the same number of ports and are configured with the same amount of memory and vCPUs.

FortiWeb-VM supports HA. However, if you do not wish to use the native HA, you can use your hypervisor or VM environment manager to install your virtual appliances over a hardware cluster to improve availability. For example, VMware clusters can use vMotion or VMware HA.

Active-pastive HA topology and failover — IP address transfer to the new active appliance

For best fault tolerance, make sure that your topology is fully redundant, with no single points of failure.

For example, in Active-pastive HA topology and failover — IP address transfer to the new active appliance, the switch, firewall, and Internet connection are all single points of failure. If any should fail, websites would be unavailable, despite the HA cluster. To prevent this, you would add a dual ISP connection to separate service providers, preferably with their own redundant pathways upstream. You would also add a standby firewall, and a standby switch.

The style of FortiWeb HA is active-passive: one appliance is elected to be the active appliance (also called the primary, main, or master), applying the policies for all connections. The other is a passive standby (also called the secondary, or slave), which assumes the role of the active appliance and begins processing connections only if the active appliance fails.

The active and standby appliances detect failures by communicating through a heartbeat link that connects the two appliances in the HA pair. Failure is assumed when the active appliance is unresponsive to the heartbeat from the standby appliance for a configured amount of time:

Heartbeat timeout = Detection Interval x Heartbeat Lost Threshold

If the active appliance fails, a failover occurs: the standby becomes active. To do this, the standby takes all IP addresses of the unresponsive appliance: it notifies the network via ARP to redirect traffic for that virtual MAC address (VMAC) to its own network interfaces. (In transparent modes, this includes the management IP. Additionally, at Layer 2, switches are notified that the VMAC is now connected to a different physical port. So even though in these modes the interfaces usually are transparent bridges without IPs, ARP traffic will still occur due to failover.)

Time required for traffic to be redirected to the new active appliance varies by your network’s responsiveness to changeover notification and by your configuration:

Total failover time = ARP Packet Numbers x ARP Packet Interval + Network responsiveness + Heartbeat timeout

For example, if:

Detection Interval is 3 (i.e. 0.3 seconds)
Heartbeat Lost Threshold is 2
ARP Packet Numbers is 3
ARP Packet Interval is 1
Network switches etc. take 2 seconds to acknowledge and redirect traffic flow

then the total time between the first unacknowledged heartbeat and traffic redirection could be up to 5.6 seconds.

When the former active appliance comes back online, it may or may not assume its former active role. For an explanation, see How HA chooses the active appliance. (At this time, when an appliance is rejoining the cluster, FortiWeb will also send gratuitous ARP packets. This helps to ensure that traffic is not accidentally forwarded to both the current and former active appliance in cases where the cluster is connected through 2 switches.)

Active-pastive HA topology and failover — IP address transfer to the new active appliance shows an example HA network topology with IP address transfer from the active appliance to the standby appliance upon failover. In this example, the primary heartbeat link is formed by a crossover cable between the two port3 physical network ports; the secondary heartbeat link is formed between the two port4 physical network ports.

To configure FortiWeb appliances that are operating in HA mode, you usually connect only to the active appliance. The active unit’s configuration is almost entirely synchronized to the passive appliance, so that changes made to the active appliance are propagated to the standby appliance, ensuring that it is prepared for a failover.

However, you can use the HA setting for a cluster member to configure it with an independent management port. You can then use the IP address of the port to directly manage the cluster member.

Tasks that can require you to access a cluster member directly include:

connecting to a standby appliance in order to view log messages recorded about the standby appliance itself on its own hard disk
connecting to a standby appliance to configure settings that are not synchronized (see Configuration settings that are not synchronized by HA)

Active-active HA topology

An active-active HA　cluster created in Reverse Proxy and True Transparent Proxy modes cab be consisted of more than two FortiWeb appliances (up to eight). Note that this is not the active-active HA deployed in WCCP mode (see Example: Using WCCP with multiple FortiWeb appliances) or an external HA/load balancer (see Example network topology: transparent proxy mode with configuration synchronization and external HA via FortiADC). All the cluster members are operating as an active appliances together to simultaneously handle the traffic between clients and the back web servers. In an active-active HA cluster, one of the member appliances will be selected as the master appliance, while the others are slaves. The master appliance in an active-active HA　cluster plays the role as the central controller to receive traffic from clients and back web servers, and distribute the traffic to all the cluster members (including itself) according specified load-balancing algorithm so that each FortiWeb appliance performs the security services to protect the traffic. Similar to the active-passive HA deployment, the operation of active-active HA cluster requires heartbeat detection, configuration and session synchronization between the cluster members. If the master appliance fails, one of the slaves will take it over. The heartbeat interfaces of all the HA appliances must be connected directly with crossover cables or through switches to carry the heartbeat and synchronization traffic between the HA cluster members.

Load-balancing in Active-active HA

There are three load-balancing algorithms available for master appliance to distribute received traffic over the available cluster members:

By source IP: consistently distribute the traffic coming from a source to the same cluster member (the default algorithm).
By connections: dynamically distribute traffic to a cluster member who has the fewest connections processing.
Round-Robin: distribute traffic among the available members in a circular order.

All the cluster members, including the master appliance, are the candidates for the algorithms, unless failure is detected on any of them. Traffic distribution is based on TCP/UDP sessions, which means once the first packet of a TCP/UDP session is assigned to a cluster member, the subsequent packets of the session will be consistently distributed to the same appliance during a time period. For more details, see How to change the load-balancing algorithm for an active-active HA cluster.

Although algorithm By source IP distribute the subsequent traffic coming from the same source IP address to a fix cluster member, it performs weighted round-robin to determine the cluster member for the first packet coming from the IP address. You can configure the weights between the cluster members through the CLI command set weight in system ha. See FortiWeb CLI Reference for details.

Fail-over in Active-active HA

An active-active HA cluster performs the same heartbeat detection and configuration synchronization mechanisms as an active-passive HA pair (see HA heartbeat & synchronization and Active-pastive HA topology and failover). If a slave failure is detected, the slave appliance will be ignored by the master for its traffic distribution. If the master fails, one of the slave appliances will take it over as a master immediately (see How HA chooses the active appliance.). After the original master recovers from failure, it becomes the slave unit. Note that all the sessions distributed to a cluster appliance will be lost if the appliance goes fail.

Session synchronization in Active-active HA

Once the master appliance fails and a slave takes it over, the subsequent traffic of all the original and new sessions will be transferred to the new master for distribution (those sessions distributed to the original master appliance by itself are not included, since the original master lost them while it failed). To distribute the original sessions in the original way, the new master has to know how they are mapped. To provide a seamless takeover for this, a master appliance must maintain the mapping information (called session information as well) for all the sessions and synchronize (see Heartbeat Interface) it to all the other cluster members all the time, so that when a slave becomes the master the subsequent traffic of the original sessions can be destined to where they were. Note that active-passive HA pair will not maintain the session synchronization.

Although session synchronization in active-active HA guarantees a seamless takeover, it brings extra CPU and bandwidth consumption as well. The session synchronization is disabled by default, and you can enable it through the CLI command set session-pickup in system ha. See FortiWeb CLI Reference for details.

To configure HA

1. If the HA cluster will use FortiGuard services, license all FortiWeb appliances in the HA group, and register them with the Fortinet Technical Support website:

https://support.fortinet.com/

If you license only the primary appliance in an HA group, after a failover, the secondary appliance will not be able to use the FortiGuard service. This could cause traffic to be scanned with out-of-date definitions, potentially allowing newer attacks.

2. Cable both appliances into a redundant network topology.

For an example, see Active-pastive HA topology and failover — IP address transfer to the new active appliance or Active-active HA topology and failover in reverse proxy mode.

3. Physically link the FortiWeb appliances that will be members of the HA cluster.

For both active-active and active-passive HA cluster, you must link at least one of their ports (e.g. port4 to port4) for heartbeat and synchronization traffic between members of the cluster. You can either:

link two appliances directly via a crossover cable (for only two appliances in a cluster)
link the appliances through a switch (for more than two appliances in a cluster)

If a switch is used to connect the heartbeat interfaces, the heartbeat interfaces must be reachable by Layer 2 multicast.

Maintain the heartbeat link(s). If the heartbeat is accidentally interrupted for an active-passive HA group, such as when a network cable is temporarily disconnected, the secondary appliance will assume that the primary unit has failed, and become the new primary appliance. If no failure has actually occurred, both FortiWeb appliances will be operating as primary appliances simultaneously. Similarly, multiple appliances will be operating as master appliances simultaneously for an active-active HA cluster.

To avoid unintentional failovers due to accidental detachment or hardware failure of a single heartbeat link, make two heartbeat links.

For example, you might link port3 to port3 on the other appliance, and link port4 to port4 on the other appliance, then configure both appliances to use those network interfaces for heartbeat and synchronization.

If you link HA appliances through switches, to improve fault tolerance and reliability, link the ports through two separate switches. Do not connect these switches to your overall network, which could introduce a potential attack point, and could also allow network load to cause latency in the heartbeat, which could cause an unintentional failover.

4. Log in to all the appliances as the admin administrator account.

Accounts whose access profile includes Read and Write permissions to the System Configuration area can configure HA, but may not be able to use features that may be necessary when using HA, such as logs and network configuration.

5. On all the appliances, go to System > Config > HA.

To access this part of the web UI, your administrator's account access profile must have Read and Write permission to items in the System Configuration category. For details, see Permissions.

By default, each FortiWeb appliance operates as a single, standalone appliance: only the Configured HA mode drop-down list appears, with the Standalone option selected.

6. From Configured HA mode, select Active-Passive if you want to create an active-passive HA group, or select Active-Actiev if you want to create an active-active HA group.

Fail-open is disabled when the FortiWeb appliance is configured as part of an HA pair. For information on fail-to-wire, see Fail-to-wire for power loss/reboots.

Additional options appear that enable you to configure HA.

7. Configure these settings:

Setting name	Description
Group-name	Type a name to identify the HA pair if you have more than one. This setting is optional, and does not affect HA function. The maximum length is 35 characters.
Device Priority	Type the priority of the appliance when selecting the active-passive primary (or active-active master) appliance in the HA cluster. (On active-passive standby or active-active slave devices, this setting can be reconfigured using the CLI command `execute ha manage <serial-number_str> <priority_int>`. For details, see the FortiWeb CLI Reference.) This setting is optional. The smaller the number, the higher the priority. The valid range is 0 to 9. The default is 5. Note: By default, unless you enable Override, uptime is more important than this setting. For details, see How HA chooses the active appliance.
Override	Enable to make Device Priority a more important factor than uptime when selecting the main appliance. See How HA chooses the active appliance.
Reserve Management Port for Cluster Member <interface name>	Specifies whether the network interface you select provides administrative access to this appliance when it is a member of the HA cluster. When this option is selected, you can access the configuration for this cluster member using the IP address of the specified network interface. The interface configuration, including administrative access and other settings, is not synchronized with other cluster members. You cannot configure routing for the port you select. To allow your management computer to connect with the web UI and CLI, ensure it is on the same subnet as the port. (Alternatively, you can configure a source IP NAT on the router or firewall that modifies the management computer's source IP.) You can configure up to 8 reserved management ports in each HA cluster.
Group ID	Type a number that identifies the HA cluster. All the members of the HA cluster must have the same group ID. If you have more than one HA cluster on the same network, each HA cluster must have a different group ID. Changing the group ID changes the cluster’s virtual MAC address. The valid range is 0 to 63. The default value is 0.
Detection Interval	Type the number of 100-millisecond intervals to set the pause between each heartbeat packet that the one FortiWeb appliance sends to the other FortiWeb appliances in the HA cluster. This is also the amount of time that a FortiWeb appliance waits before expecting to receive a heartbeat packet from the other appliances. This part of the configuration is synchronized between the all the appliances in a cluster. The valid range is 1 to 20 (that is, between 100 and 2,000 milliseconds). Note: Although this setting is synchronized between all the appliances, you should initially configure all the appliances with the same Detection Interval to prevent inadvertent failover from occurring before the initial synchronization.
Heartbeat Lost Threshold	Type the number of times one of HA appliances retries the heartbeat and waits to receive HA heartbeat packets from the other HA appliances before assuming that the other appliances have failed. This part of the configuration is synchronized between all the appliances in a cluster. Normally, you do not need to change this setting. Exceptions include: Increase the failure detection threshold if a failure is detected when none has actually occurred. For example, during peak traffic times, if the master appliance is very busy, it might not respond to heartbeat packets in time, and the slave appliances may assume that the master appliance has failed. Reduce the failure detection threshold or detection interval if administrators and HTTP clients have to wait too long before being able to connect through the master appliance, resulting in noticeable down time. The valid range is from 1 to 60. Note: Although this setting is synchronized between all the appliances, you should initially configure all the appliances with the same Heartbeat Lost Threshold to prevent inadvertent failover from occurring before the initial synchronization.
Port Monitor	Mark the check boxes of one or more network interfaces that each directly correlate with a physical link. These ports will be monitored for link failure. Port monitoring (also called interface monitoring) monitors physical network ports to verify that they are functioning properly and linked to their networks. If the physical port fails or the cable becomes disconnected, a failover occurs. You can monitor physical interfaces, but not VLAN subinterfaces or 4-port switches. If you select a link aggregate interface, failover occurs only if all the physical network interfaces in the logical interface fail. For more information, see Link aggregation. Note: To prevent an unintentional failover, do not configure port monitoring until you configure HA on all the appliances in the HA cluster, and have plugged in the cables to link the physical network ports that will be monitored.
Heartbeat Interface	Select which port(s) on this appliance that the all the appliances will use to send heartbeat signals and synchronization data (configuration synchronization for active-passive HA, or configuration and session synchronization for active-active HA) between each other (i.e. the HA heartbeat link). Connect this port to the same port number on the other HA cluster members. (e.g., If you select port3 for the primary heartbeat link, connect port3 on this appliance to port3 on the other appliances.) At least one heartbeat interface must be selected on each appliance in the HA cluster. Ports that currently have an IP address assigned for other purposes (that is, virtual servers or bridges) cannot be re-used as a heartbeat link. Tip: If enough ports are available, you can select both a primary heartbeat interface and a secondary heartbeat interface on each appliance in the HA pair to provide heartbeat link redundancy. (You cannot use the same port as both the primary and secondary heartbeat interface on the same appliance, as this is incompatible with the purpose of link redundancy.) Note: If a switch is used to connect the heartbeat interfaces, the heartbeat interfaces must be reachable by Layer 2 multicast. Note: The master appliance use the heartbeat interface to synchronize its session table to other appliances in an active-active HA cluster by default. However, you can use extra interfaces for the session synchronization by configuring `set session-sync-dev <port_number>` in CLI command `config system ha`. Moreover, the appliance synchronizes sessions to others in unicase by default, but you can choose broadcast for it by configuring `set session-sync-broadcast {enable\|disable}` in CLI command `config system ha`. Broadcast will be suggested if a active-active HA cluster contains many appliances. For details, see the FortiWeb CLI Reference.

8. Click Apply.

All the appliances join the HA cluster by matching their Group ID. They begin to send heartbeat and synchronization traffic to each other through their heartbeat links.

To determine which appliance currently has the role of the main appliance, on System > Config > HA-Config, in the HA Member table, view the HA Role column:

main — The appliance in this row is currently active. The active appliance applies policies to govern the traffic passing to your web servers. Also called the primary, master, or main appliance.
standby — The appliance in this row is currently passive, and is not actively applying policies. The passive appliance listens to heartbeat traffic and port monitoring for signs that the main appliance may have become unresponsive, at which point it will assume the role of the main appliance. Also called the secondary or standby appliance.

If both appliances believe that they are the main:

Test the cables and/or switches in the heartbeat link to verify that the link is functional.
Verify that you have selected the heartbeat port or ports in Heartbeat Interface. Make sure that the primary and secondary link is not crossed (that is, the primary heartbeat interface is not connected to the secondary heartbeat interface on the other appliance).
Verify that the Group ID matches on both appliances.
Verify that the ports on Port Monitor are linked and up (available).
If the heartbeat link passes through switches and/or routers, you may need to adjust the time required after a reboot to assess network availability before electing the main appliance. For details, see the boot-time <seconds_int> setting in the FortiWeb CLI Reference.
For debugging logs, use the diagnose system ha status and diagnose debug application hatalk level commands. For details, see the FortiWeb CLI Reference.

9. To monitor the HA cluster for failover, you can use SNMP (see Configuring an SNMP community), log messages, and alert email (see Configuring logging).

If failover time is too long, adjust the following:

Setting name	Description
ARP Packet Numbers	Type the number of times that the FortiWeb appliance will broadcast extra address resolution protocol (ARP) packets when it takes on the main role. (Even though a new NIC has not actually been connected to the network, FortiWeb does this to notify the network that a new physical port has become associated with the IP address and virtual MAC of the HA pair.) This is sometimes called “using gratuitous ARP packets to train the network,” and can occur when the main appliance is starting up, or during a failover. Also configure ARP Packet Interval. Normally, you do not need to change this setting. Exceptions include: Increase the number of times the main appliance sends gratuitous ARP packets if your HA pair takes a long time to fail over or to train the network. Sending more gratuitous ARP packets may help the failover to happen faster. Decrease the number of times the main appliance sends gratuitous ARP packets if your HA pair has a large number of VLAN interfaces and virtual domains. Because gratuitous ARP packets are broadcast, sending them may generate a large amount of network traffic. As long as the HA pair still fails over successfully, you could reduce the number of times gratuitous ARP packets are sent to reduce the amount of traffic produced by a failover. The valid range is 1 to 16.
ARP Packet Interval	Type the number of seconds to wait between each broadcast of ARP packets. Normally, you do not need to change this setting. Exceptions include: Decrease the interval if your HA pair takes a long time to fail over or to train the network. Sending ARP packets more frequently may help the failover to happen faster. Increase the interval if your HA pair has a large number of VLAN interfaces and virtual domains. Because gratuitous ARP packets are broadcast, sending them may generate a large amount of network traffic. As long as the HA pair still fails over successfully, you could increase the interval between when gratuitous ARP packets are sent to reduce the rate of traffic produced by a failover. The valid range is from 1 to 20.

Setting name

Description

ARP Packet Numbers

Type the number of times that the FortiWeb appliance will broadcast extra address resolution protocol (ARP) packets when it takes on the main role. (Even though a new NIC has not actually been connected to the network, FortiWeb does this to notify the network that a new physical port has become associated with the IP address and virtual MAC of the HA pair.) This is sometimes called “using gratuitous ARP packets to train the network,” and can occur when the main appliance is starting up, or during a failover. Also configure ARP Packet Interval.

Normally, you do not need to change this setting. Exceptions include:

Increase the number of times the main appliance sends gratuitous ARP packets if your HA pair takes a long time to fail over or to train the network. Sending more gratuitous ARP packets may help the failover to happen faster.
Decrease the number of times the main appliance sends gratuitous ARP packets if your HA pair has a large number of VLAN interfaces and virtual domains. Because gratuitous ARP packets are broadcast, sending them may generate a large amount of network traffic. As long as the HA pair still fails over successfully, you could reduce the number of times gratuitous ARP packets are sent to reduce the amount of traffic produced by a failover.

The valid range is 1 to 16.

ARP Packet Interval

Type the number of seconds to wait between each broadcast of ARP packets.

Normally, you do not need to change this setting. Exceptions include:

Decrease the interval if your HA pair takes a long time to fail over or to train the network. Sending ARP packets more frequently may help the failover to happen faster.
Increase the interval if your HA pair has a large number of VLAN interfaces and virtual domains. Because gratuitous ARP packets are broadcast, sending them may generate a large amount of network traffic. As long as the HA pair still fails over successfully, you could increase the interval between when gratuitous ARP packets are sent to reduce the rate of traffic produced by a failover.

The valid range is from 1 to 20.

10. How to change the load-balancing algorithm for an active-active HA cluster:

The previous configurations are mostly the same for both active-passive HA pair and active-active HA cluster; however, you might want to change the load-balancing algorithm from default for an active-active HA cluster. You can change the algorithm by configuring set schedule {ip | leastconnection | round-robin} in CLI command config system ha. For details, see the FortiWeb CLI Reference.

Note: FortiWeb's Session Management (see Session Management) is not supposed by the active-active HA deployment with the algorithm By connections or Round-robin being used for the load-balancing.

If your HA link passes through switches and/or routers, and inadvertent failovers occur when rebooting the HA pair, you can increase the maximum time to wait for a heartbeat signal after a reboot by configuring boot‑time <limit_int>. See the FortiWeb CLI Reference.

Check your HA topology information and statistics

After completing your HA deployment, you can manage the HA topology and view information and statistics for each HA unit.

Go to System > Status > HA Topology. From here, you can select the master unit or slaves in the cluster, and a pop-up window will appear with the option to disconnect them. If you select a slave in the cluster, the pop-up will also provide options to view its attack logs, event logs, and traffic logs. To view logs for the master unit in the cluster, go to Log&Report > Log Access and select the log(s) you want to view.

From System > Status > HA Topology, click View HA Statistics in the top right corner of the window. The following information about each unit in the cluster is displayed: