Found it! -- http://www.cisco.com/en/US/products/hw/switches/ps4324/products_module_installation_guide_chapter09186a008009c173.html#wp1026199
"Hot-Swapping Feature
Catalyst 4500 series switches allow you to remove and replace switching modules without powering down the switch. This feature is known as hot swapping.
When you remove or insert a switching module while the switch is operating, the system does the following:
1. Scans the backplane for configuration changes.
2. Initializes all newly inserted switching modules, notes any removed modules, and places them in the administratively shutdown state.
3. Places any previously configured interfaces on the switching module back to the state they were in when they were removed. Any newly inserted interfaces are put in the administratively shutdown state, as if they were present (but unconfigured) at boot time. If you insert a similar switching-module type into a slot, its ports are configured and brought online up to the port count of the original switching module.
The system runs diagnostic tests on any new interfaces. If the test passes, the system is operating normally. If the new switching module is faulty, the system resumes normal operation but places the new module in the "faulty" state.
If the diagnostic test fails, the system crashes, which usually indicates that the new switching module has a problem and should be removed.
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Caution To avoid erroneous failure messages, allow at least 15 seconds for the system to reinitialize, and note the current configuration of all interfaces before you remove or insert another switching module.
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When you hot swap switching modules, the system displays status messages on the console screen. The following sample display shows the messages logged by the system when a switching module is removed from slot 2:
Console> (enable)
2001 Sep 09 12:23:26 %SYS-5-MOD_REMOVE:Module 3 has been removed
Console> (enable)
2001 Sep 09 12:23:44 %SYS-5-MOD_INSERT:Module 3 has been inserted
Console> (enable)
2001 Sep 09 12:23:47 %SYS-5-MOD_OK:Module 3 is online
Console> (enable)
If you use the show port command to query the module before reinstalling a module to replace the removed one, the system responds, "Module 3 is not installed." When the module is reinserted, the system recognizes the module as ready again.
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Please rate helpful posts, thanks!
David Swafford.
