High Availability; Overview - D-Link NetDefendOS User Manual

Chapter 11: High Availability
This chapter describes the high availability fault-tolerance feature in NetDefend Firewalls.
• Overview, page 820
• HA Mechanisms, page 823
• Setting Up HA, page 827
• HA Issues, page 834
• Upgrading an HA Cluster, page 837
• Link Monitoring and HA, page 839
• HA Advanced Settings, page 840

11.1. Overview

HA Clusters
NetDefendOS High Availability (HA) provides a fault tolerant capability for NetDefend Firewall
installations. HA works by adding a back-up slave NetDefend Firewall to an existing master
firewall. The master and slave are connected together by a synchronization link and make up a
logical HA Cluster. One of the units in a cluster will be active while the other unit will be inactive
and on standby.
Initially, the cluster slave will be inactive and will only monitor the activity of the master. If the
slave detects that the master has become inoperative, an HA failover takes place and the slave
becomes active, assuming processing responsibility for all traffic. If the master later becomes
operative again, the slave will continue to be active but the master will now monitor the slave
with failover only taking place if the slave fails. This is sometimes known as an active-passive
implementation of fault tolerance.
Note: HA is not available on all NetDefend models
The HA feature is not available on the DFL-260E and DFL-860E.
820