Hi,
All Catalyst 4500 series switches support hot swapping, which lets you install, remove, replace, and rearrange switching modules without turning off the system power. When the system detects that a switching module has been installed or removed, it runs diagnostic and discovery tests automatically, acknowledges the presence or absence of the module, and resumes system operation with no operator intervention.
http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/hardware/configuration/notes/gMdCf_nt.html
HTH,
Lei Tian
