Cisco Cisco IOS Software Release 12.4(20)YA

© 2009 Cisco Systems, Inc. All rights reserved.

These release notes describe new features and significant software components for the 
Cisco Secure Router 500 series that support the Cisco IOS Release 12.4(20)YA releases. These release 
notes are updated as needed. Use these release notes with the 

Cisco IOS Release 12.4T and About Cisco IOS Release Notes.

For a list of the software caveats that apply to the Release 12.4(20)YA releases, see the 

. See also 

The online caveats document is updated 

for every maintenance release.