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User Guide for Cisco Secure ACS for Windows Server
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Chapter 9      System Configuration: Advanced
CiscoSecure Database Replication
c. The primary Cisco Secure ACS verifies that the version of Cisco Secure 
ACS that the secondary Cisco Secure ACS is running is the same as its 
own version of Cisco Secure ACS. If not, replication fails.
d. The primary Cisco Secure ACS compares the list of database 
components it is configured to send with the list of database components 
the secondary Cisco Secure ACS is configured to receive. If the 
secondary Cisco Secure ACS is not configured to receive any of the 
components that the primary Cisco Secure ACS is configured to send, the 
database replication fails.
3. After the primary Cisco Secure ACS has determined which components to 
send to the secondary Cisco Secure ACS, the replication process continues on 
the primary Cisco Secure ACS as follows:
a. The primary Cisco Secure ACS stops its authentication and creates a 
copy of the CiscoSecure database components that it is configured to 
replicate. During this step, if AAA clients are configured properly, those 
that usually use the primary Cisco Secure ACS failover to another 
Cisco Secure ACS.
b. The primary Cisco Secure ACS resumes its authentication service. It also 
compresses and encrypts the copy of its database components for 
transmission to the secondary Cisco Secure ACS.
c. The primary Cisco Secure ACS transmits the compressed, encrypted 
copy of its database components to the secondary Cisco Secure ACS. 
This transmission occurs over a TCP connection, using port 2000. The 
TCP session uses a 128-bit encrypted, Cisco-proprietary protocol.
4. After the preceding events on the primary Cisco Secure ACS, the database 
replication process continues on the secondary Cisco Secure ACS as follows:
a. The secondary Cisco Secure ACS receives the compressed, encrypted 
copy of the CiscoSecure database components from the primary 
Cisco Secure ACS. After transmission of the database components is 
complete, the secondary Cisco Secure ACS decompresses the database 
components.
b. The secondary Cisco Secure ACS stops its authentication service and 
replaces its database components with the database components it 
received from the primary Cisco Secure ACS. During this step, if AAA 
clients are configured properly, those that usually use the secondary 
Cisco Secure ACS failover to another Cisco Secure ACS.