High Availability

Polling

The High Availability function provides an optional polling feature that can be configured through the CLI. Polling is used to determine the regular heartbeat mechanism between the standby device and the active device. This function provides the following configuration parameters:

•Poll-timerdetermines the period in seconds that the standby device polls the active device. This, in turn, determines how quickly the standby device will detect that the active device has failed.

The active device should immediately respond to a poll from the standby device. If it does not, the standby device will retransmit the heartbeat message after a specified wait-interval in milliseconds.

A low poll timer increases the load on the network and can cause the standby device to become active due to lost poll requests or responses.

•Retry-countdetermines how many heartbeats the standby will send before it determines that the active device is not responding. If the active device does not respond to the heartbeats on any of the IP interfaces, the standby device will become the active device.

For details on configuring the high-availability polling feature, see the Command Line Interface Reference.

Configuration Overview

To use high availability, you need to configure a unique HA management IP address that can be used to manage the device from the network regardless of whether the device is in an active or passive state. In addition, we recommend that you configure a HA management IP address for each internal and external interface on the device. The IP addresses must conform to the following rules:

•The IP address for the external interface must be a static IP address.

•Each HA management IP addresses must be on the same IP subnet as it’s respective IP interface.

When the devices are configured for High Availability, the devices use the HA management IP addresses to talk to each other and monitor the current state.

The following figure illustrates a simple HA deployment configured with a single IP interface and external IP interface.

Figure 8–5: High Availability Configuration

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