Cisco GLBP

I am trying to implement Cisco GLBP on 2 Cisco 2821 routers with the following setup (see diagram below).

As when I link up the 2 Cisco2821 without going thru the switch I am able to ping to both Cisco2821 and also to the virtual ip.

Cisco2821(1)– Core Router1 –Cisco2821(2)

While both Cisco2921 connects to a single Cisco3750

Can anyone one advise if such setup is possible and if possible what are the configuration I need to look into on the switch (on the 2 ports connected to the 2 Cisco2821)?