To avoid unnecessary takeovers and to minimize the chance of split-brain situations, you can configure additional heartbeat interfaces in syslog-ng Store Box (SSB). These interfaces are used only to detect that the other node is still available, they are not used to synchronize data between the nodes (only heartbeat messages are transferred). For example, if the main HA interface breaks down, or is accidentally unplugged and the nodes can still access each other on the redundant HA interface, no takeover occurs, but no data is synchronized to the secondary node until the main HA link is restored. Similarly, if connection on the redundant heartbeat interface is lost, but the main HA connection is available, no takeover occurs.

If a redundant heartbeat interface is configured, its status is displayed in the Basic Settings > High Availability > Redundant Heartbeat status field, and also in the HA > Redundant field of the System monitor. For a description of each possible status, see Understanding SSB cluster statuses.

The redundant heartbeat interface is a virtual interface with a virtual MAC address that uses an existing interface of SSB (for example, the external or the management interface). The MAC address of the virtual redundant heartbeat interface is displayed as HA MAC.

The MAC address of the redundant heartbeat interface is generated in a way that it cannot interfere with the MAC addresses of physical interfaces. Similarly, the HA traffic on the redundant heartbeat interface cannot interfere with any other traffic on the interface used.

If the nodes lose connection on the main HA interface, and after a time the connection is lost on the redundant heartbeat interfaces as well, the secondary node becomes active. However, as the primary node was active for a time when no data synchronization was possible between the nodes, this results in a split-brain situation which must be resolved before the HA functionality can be restored. For details, see Recovering from a split brain situation.

SSB nodes use UDP port 694 to send each other heartbeat signals.

The following describes how to configure a redundant heartbeat interface.

To configure a redundant heartbeat interface

1. Navigate to Basic Settings > High Availability > Redundant heartbeat.

2. Enable the interface you want to use as redundant heartbeat interface (for example, External interface). Using an interface as a redundant heartbeat interface does not affect the original traffic of the interface.

   Figure 62: Basic Settings > High Availability > Redundant heartbeat — Configuring redundant heartbeat interfaces

   

3. Enter an IP address into the This node > Redundant heartbeat > Interface IP field of the selected interface.

   NOTE: Consider the following:

   • The two nodes must have different Interface IP.

   • If you do not use next hop monitoring on the redundant interface, you can use any Interface IP (even if otherwise it does not exist on that network).

   • If you use next hop monitoring on the redundant interface, the Interface IP address must be a real IP address that is visible from the other node.

   • If you use next hop monitoring on the redundant interface, the Interface IP must be accessible from the next-hop address, and vice-versa. For details on next hop monitoring, see Next-hop router monitoring.

4. Enter an IP address into the Other node > Redundant heartbeat > Interface IP field of the selected interface.

   NOTE: Consider the following:

   • The two nodes must have different Interface IP.

   • If you do not use next hop monitoring on the redundant interface, you can use any Interface IP (even if otherwise it does not exist on that network).

   • If you use next hop monitoring on the redundant interface, the Interface IP address must be a real IP address that is visible from the other node.

   • If you use next hop monitoring on the redundant interface, the Interface IP must be accessible from the next-hop address, and vice-versa. For details on next hop monitoring, see Next-hop router monitoring.

5. Repeat the previous steps to add additional redundant heartbeat interfaces if needed.

6. Click .

7. Restart the nodes for the changes to take effect: click Reboot Cluster.