http://www.cisco.com/en/US/products/ps6550/prod_presentation0900aecd801790a3.html
SUPPORTED PLATFORMS
GLBP is supported on the following hardware platforms:
? Cisco 1700 Series Routers
? Cisco 2600 Series Routers s
? Cisco 3640 Router
? Cisco 3660 Router
? Cisco 3725 Router
? Cisco 3745 Router
? Cisco 7200 Series Routers
? Cisco 7300 Series Routers
? Cisco 7500 Series Routers
? Cisco 7600 Series Routers
? Cisco Catalyst? 6500 Series Switches
Above states that it's not supported in Cat4000 at all at this time. It's in the road-map, however, unfortunately I have no timetable information.
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