HAL, or High Availability L2TP, is a new feature that was added in the factory release version 1.54. The feature gives extra resilience and near zero packetloss when you have multiple L2TP tunnels between sites by duplicating and de-duplicating packets over multiple L2TP tunnels between FireBricks. We've created a Knowledge base article on the feature: Knowledge base - High Availability L2TP.
