What method can be used to ensure high availability in Sophos XG Firewall deployment?

The method to ensure high availability in a Sophos XG Firewall deployment is through clustering, which can be set up in either active-passive or active-active configurations.

In an active-passive setup, one firewall node is designated as the primary node, handling all the traffic, while the secondary node remains on standby, ready to take over if the primary fails. This redundancy is crucial for maintaining network availability, as it allows for seamless failover. On the other hand, in an active-active configuration, both nodes actively handle traffic, effectively distributing the load while providing redundancy. This not only ensures high availability but can also improve performance due to load balancing.

Using a backup server, as mentioned in the first choice, does not provide the same level of dynamic redundancy. While backups are essential for data recovery, they do not facilitate real-time failover during active sessions. Increasing the firewall's CPU might improve performance but does not inherently add to availability, while reducing firewall rules could potentially improve processing speed but doesn’t contribute to redundancy or failover capabilities.

In summary, clustering in active-passive or active-active setups is the most effective method for ensuring high availability, allowing for continuous operation and immediate response in the event of hardware or node failure.