6.2.3. Procedure – Next-hop router monitoring

Purpose: 

By default, HA takeover occurs only if the master node stops working or becomes unreachable from the slave node. However, this does not cover the scenario when the master node becomes unaccessible to the outside world while the slave node would be still accessible (for example because it is connected to a different router).

To address such situations, you can specify IP addresses (usually next hop routers) to continuously monitor from both the master and the slave nodes using ICMP echo (ping) messages. One such address can be set up for every interface.

When setting up next hop monitoring, you have to make sure that the master and slave nodes can ping the specified address directly. You can either:

  • Choose the addresses of the redundant-HA PSM interfaces so that they are on the same subnet as the next-hop address

  • Configure the next-hop device with an additional IP-address that is on the same subnet as the redundant-HA PSM interfaces facing it

If any of the monitored addresses becomes unreachable from the master node while being reachable from the slave node (in other words, more monitored addresses are accessible from the slave node) then it is assumed that the master node is unreachable and a forced takeover occurs — even if the master node is otherwise functional.

Naturally, if the slave node is not capable of taking over the master node (for example because there is data not yet synchronized from the current master node) no takeover is performed.

To configure next hop monitoring, complete the following steps.

Steps: 

  1. Navigate to Basic Settings > High Availability > Next hop monitoring.

  2. Select the interface to use for monitoring its next-hop router.

    Figure 6.6. Basic Settings > High Availability — Configuring next hop monitoring

    Basic Settings > High Availability — Configuring next hop monitoring
  3. Enter the IP address to monitor from the current master node (for example the IP address of the router or the switch connected to the interface) into the This node > Next hop IP field of the selected interface. This IP address must be a real IP address that is visible from the interface, and must be on the same local network segment.

    Use an IPv4 address.

  4. Enter the IP address to monitor from the current slave node (for example the IP address of the router or the switch connected to the interface) into the Other node > Next hop IP field of the selected interface. This IP address must be a real IP address that is visible from the interface, and must be on the same local network segment.

    Use an IPv4 address.

  5. Repeat the previous steps to add IP addresses to be monitored from the other interfaces if needed.

  6. Click .

    Warning

    For the changes to take effect, you have to restart both nodes. To restart both nodes, click Reboot Cluster.