1-16
Cisco ASA Series CLI Configuration Guide
Chapter 1 Configuring a Cluster of ASAs
Information About ASA Clustering
New Connection Ownership
When a new connection is directed to a member of the cluster via load balancing, that unit owns both
directions of the connection. If any connection packets arrive at a different unit, they are forwarded to
the owner unit over the cluster control link. For best performance, proper external load balancing is
required for both directions of a flow to arrive at the same unit, and for flows to be distributed evenly
between units. If a reverse flow arrives at a different unit, it is redirected back to the original unit. For
more information, see the
“Load Balancing Methods” section on page 1-12
Sample Data Flow
The following example shows the establishment of a new connection.
1.
The SYN packet originates from the client and is delivered to an ASA (based on the load balancing
method), which becomes the owner. The owner creates a flow, encodes owner information into a
SYN cookie, and forwards the packet to the server.
2.
The SYN-ACK packet originates from the server and is delivered to a different ASA (based on the
load balancing method). This ASA is the forwarder.
3.
Because the forwarder does not own the connection, it decodes owner information from the SYN
cookie, creates a forwarding flow to the owner, and forwards the SYN-ACK to the owner.
4.
The owner sends a state update to the director, and forwards the SYN-ACK to the client.
5.
The director receives the state update from the owner, creates a flow to the owner, and records the
TCP state information as well as the owner. The director acts as the backup owner for the
connection.
6.
Any subsequent packets delivered to the forwarder will be forwarded to the owner.
7.
If packets are delivered to any additional units, it will query the director for the owner and establish
a flow.
8.
Any state change for the flow results in a state update from the owner to the director.
Client
SYN/ACK
1. SYN
1. SYN
2. SYN/ACK
4. State
update
3. SYN/ACK
Director
Cluster
Server
Owner
Forwarder
After step 4, all
remaining packets
are forwarded
directly to the owner.
333480
Inside
Outside
Summary of Contents for 5505 - ASA Firewall Edition Bundle
Page 28: ...Glossary GL 24 Cisco ASA Series CLI Configuration Guide ...
Page 61: ...P A R T 1 Getting Started with the ASA ...
Page 62: ......
Page 219: ...P A R T 2 Configuring High Availability and Scalability ...
Page 220: ......
Page 403: ...P A R T 2 Configuring Interfaces ...
Page 404: ......
Page 499: ...P A R T 2 Configuring Basic Settings ...
Page 500: ......
Page 533: ...P A R T 2 Configuring Objects and Access Lists ...
Page 534: ......
Page 601: ...P A R T 2 Configuring IP Routing ...
Page 602: ......
Page 745: ...P A R T 2 Configuring Network Address Translation ...
Page 746: ......
Page 845: ...P A R T 2 Configuring AAA Servers and the Local Database ...
Page 846: ......
Page 981: ...P A R T 2 Configuring Access Control ...
Page 982: ......
Page 1061: ...P A R T 2 Configuring Service Policies Using the Modular Policy Framework ...
Page 1062: ......
Page 1093: ...P A R T 2 Configuring Application Inspection ...
Page 1094: ......
Page 1191: ...P A R T 2 Configuring Unified Communications ...
Page 1192: ......
Page 1333: ...P A R T 2 Configuring Connection Settings and QoS ...
Page 1334: ......
Page 1379: ...P A R T 2 Configuring Advanced Network Protection ...
Page 1380: ......
Page 1475: ...P A R T 2 Configuring Modules ...
Page 1476: ......
Page 1549: ...P A R T 2 Configuring VPN ...
Page 1550: ......
Page 1965: ...P A R T 2 Configuring Logging SNMP and Smart Call Home ...
Page 1966: ......
Page 2059: ...P A R T 2 System Administration ...
Page 2060: ......
Page 2098: ...1 8 Cisco ASA Series CLI Configuration Guide Chapter 1 Troubleshooting Viewing the Coredump ...
Page 2099: ...P A R T 2 Reference ...
Page 2100: ......