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Cisco ASA Series CLI Configuration Guide
Chapter 1 Setting General VPN Parameters
Understanding Load Balancing
VPN Load-Balancing Algorithm
The master device maintains a sorted list of backup cluster members in ascending IP address order. The
load of each backup cluster member is computed as an integer percentage (the number of active
sessions). AnyConnect inactive sessions do not count towards the SSL VPN load for load balancing. The
master device redirects the IPsec and SSL VPN tunnel to the device with the lowest load until it is 1
percent higher than the rest. When all backup cluster members are 1% higher than the master, the master
device redirects to itself.
For example, if you have one master and two backup cluster members, the following cycle applies:
Note
All nodes start with 0%, and all percentages are rounded half-up.
1.
The master device take s the connection if all members have a load at 1% higher than the master.
2.
If the master does not take the connection, the session is taken by whichever backup device has the
least load percentage.
3.
If all members have the same percentage load, the backup device with the least number of sessions
gets the session.
4.
If all members have the same percentage load and the same number of sessions, the device with the
least IP addresses gets the session.
VPN Load-Balancing Cluster Configurations
A load-balancing cluster can consist of ASAs of the same release, of mixed releases, as well as VPN
3000 concentrators, or a mixture of these, subject to the following restrictions:
•
Load-balancing clusters that consist of same release ASAs or all VPN 3000 concentrators can run
load balancing for a mixture of IPsec, AnyConnect, and clientless SSL VPN sessions.
•
Load-balancing clusters that consist of both same release ASAs and VPN 3000 concentrators can
run load balancing for a mixture of IPsec, AnyConnect, and clientless SSL VPN client and clientless
sessions.
•
Scenario 1: Mixed Cluster with No SSL VPN Connections
,
illustrates this situation.
Since Release 7.1(1), IPsec and SSL VPN sessions count or weigh equally in determining the load that
each device in the cluster carries. This is a change from the load-balancing calculation for the ASA
Release 7.0(x) software and the VPN 3000 concentrator. Both platforms use a weighting algorithm that
on some hardware platforms calculates the SSL VPN session load differently from the IPsec session
load.
The virtual master of the cluster assigns session requests to the members of the cluster. The ASA regards
all sessions, SSL VPN or IPsec, as equal and assigns them accordingly. You can configure the number
of IPsec and SSL VPN sessions to allow up to the maximum allowed by your configuration and license.
See
Configuring VPN Session Limits
for a description of how to set these limits.
We have tested up to ten nodes in a load-balancing cluster. Larger clusters might work, but we do not
officially support such topologies.
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: ......