Cisco Catalyst 3550 Command Reference Manual page 29

Chapter 2 Cisco IOS Commands
access-list hardware program nonblocking
Use the access-list hardware program nonblocking global configuration command to cause the system
to continue to forward frames even while a new security access-control list (ACL) configuration is being
programmed into the hardware. Use the no form of this command to return to the default behavior, where
traffic is blocked on affected interfaces when changes are made to the security ACL configuration while
the hardware is updated with the new configuration.
Syntax Description This command has no arguments or keywords.
Defaults
Traffic is blocked on affected interfaces while a new ACL configuration is loaded into hardware.
Command Modes Global configuration
Command History Release
12.1(11)EA1
Usage Guidelines By default, when changes are made to the configuration of security ACLs, the system completely blocks
traffic on the affected ports or VLANs while it is updating the hardware to the new configuration. This
includes any changes that affect the ternary content addressable memory (TCAM), including applying
an ACL to an interface or making changes to VLAN maps or ACLs that are used for security features.
This prevents the possibility of forwarding frames that should have been dropped because a partially
loaded configuration permitted a frame that the complete configuration would have blocked.
You can use the access-list hardware program nonblocking command to set the system to continue to
forward frames while a new security ACL configuration is being programmed into the hardware.
Enabling this setting might cause less disruption to traffic that should be allowed while the hardware is
being updated, but might also temporarily allow some traffic that would be denied when the new
configuration is completely loaded.
Examples This example shows how to set the system to continue forwarding frames while a new security ACL
configuration is being programmed into hardware:
Switch (config)# access-list hardware program nonblocking
You can verify your setting by entering the show running-config | include access-list hardware
privileged EXEC command.
78-11195-09
access-list hardware program nonblocking
no access-list hardware program nonblocking
Modification
This command was first introduced.
access-list hardware program nonblocking
Catalyst 3550 Multilayer Switch Command Reference
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