Firewalls are perimeter security solutions that are useful to address the unwanted traffic problem. However, fire - walls cover network security aspects at the cost of introduc ing more problems in terms of network performance, availabilit y and complexity that also need to be appropriately addressed . This work surveys existing cluster-based fault-tolerant fi rewall architectures and it discusses their trade-offs in perform ance, availability and complexity. We present preliminary evalu ation of these architectures and we also discuss the need for state - replication in stateful firewall clusters.