1-2
Cisco ASA Series CLI Configuration Guide
Chapter 1 Configuring a Cluster of ASAs
Information About ASA Clustering
• How the ASA Cluster Manages Connections, page 1-15
• ASA Features and Clustering, page 1-17
How the ASA Cluster Fits into Your Network
The cluster consists of multiple ASAs acting as a single unit. (See the “Licensing Requirements for ASA
Clustering” section on page 1-23 for the number of units supported per model). To act as a cluster, the
ASAs need the following infrastructure:
• Isolated, high-speed backplane network for intra-cluster communication, known as the cluster
control link. See the “Cluster Control Link” section on page 1-6.
• Management access to each ASA for configuration and monitoring. See the “ASA Cluster
Management” section on page 1-10.
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:
• Spanned EtherChannel (Recommended)—Interfaces on multiple members of the cluster are
grouped into a single EtherChannel; the EtherChannel performs load balancing between units. See
the “Spanned EtherChannel (Recommended)” section on page 1-12.
• Policy-Based Routing (Routed firewall mode only)—The upstream and downstream routers perform
load balancing between units using route maps and ACLs. See the “Policy-Based Routing (Routed
Firewall Mode Only)” section on page 1-14.
• 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. See the
“Equal-Cost Multi-Path Routing (Routed Firewall Mode Only)” section on page 1-15.
Performance Scaling Factor
When you combine multiple units into a cluster, you can expect a performance of approximately:
• 70% of the combined throughput
• 60% of maximum connections
• 50% of connections per second
For example, for throughput, the ASA 5585-X with SSP-40 can handle approximately 10 Gbps of real
world firewall traffic when running alone. For a cluster of 8 units, the maximum combined throughput
will be approximately 70% of 80 Gbps (8 units x 10 Gbps): 56 Gbps.
Cluster Members
• ASA Hardware and Software Requirements, page 1-3
• Bootstrap Configuration, page 1-3
• Master and Slave Unit Roles, page 1-3
• Master Unit Election, page 1-3