Cisco Cisco IOS Software Release 12.4(20)YA

Cisco IOS Release 12.4(20)YA supports the following routers: 

Cisco 851

Cisco 857

Cisco 861

Cisco 876 

Cisco 871

Cisco 877

Cisco 878

Cisco 881

Cisco 888

For detailed descriptions of new hardware features and which features are supported on each router, see 
the 

To determine the version of Cisco IOS software currently running on your Cisco 800 series router, see 
About Cisco IOS Release Notes located at 

For general information about upgrading to a new software release, see About Cisco IOS Release Notes 
located at 

For information about Feature Set Tables, see About Cisco IOS Release Notes located at 

There are no new hardware features in this release.