Cisco Cisco IOS Software Release 12.4(4)T

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Flexible Packet Matching (FPM) is the next generation access control list (ACL) pattern matching tool, 
providing more thorough and customized packet filters. FPM enables users to match on arbitrary bits of 
a packet at an arbitrary depth in the packet header and payload. FPM removes constraints to specific 
fields that had limited packet inspection.

FPM is useful because it enables users to create their own stateless packet classification criteria and to 
define policies with multiple actions (such as drop, log, or send Internet Control Message Protocol 
[ICMP] unreachable

1

) to immediately block new viruses, worms, and attacks.

Your Cisco IOS software release may not support all of the features documented in this module. To reach 
links to specific feature documentation in this module and to see a list of the releases in which each feature is 
supported, use the 

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS 
software image support. To access Cisco Feature Navigator, go to 

. An 

account on Cisco.com is not required.

1. Send ICMP unreachable is currently not supported on the Supervisor Engine 32 PISA.