How the Cluster Fits into Your Network
The cluster consists of multiple firewalls acting as a single unit. To act as a cluster, the firewalls need the following infrastructure:
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Isolated, high-speed backplane network for intra-cluster communication, known as the cluster control link.
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Management access to each firewall for configuration and monitoring.
When you place the cluster in your network, the upstream and downstream routers need to be able to load-balance the data coming to and from the cluster using one of the following methods:
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Spanned EtherChannel (Recommended)—Interfaces on multiple members of the cluster are grouped into a single EtherChannel; the EtherChannel performs load balancing between units.
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Policy-Based Routing (Routed firewall mode only)—The upstream and downstream routers perform load balancing between units using route maps and ACLs.
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Equal-Cost Multi-Path Routing (Routed firewall mode only)—The upstream and downstream routers perform load balancing between units using equal cost static or dynamic routes.