The link below only mentions 802.1Q but I believe it is a typo.
"Be aware that 802.1Q requires the Cisco Catalyst 4948, the Cisco Catalyst 4948-10GE, or the Catalyst 4500 series switch supervisor engines II-Plus-10GE V, or V-10GE; Layer 2 protocol tunneling is supported on all supervisor engines."
I'm pretty sure its not supported on the SupIV and only on certain Sup engines. Can someone confirm? Thanks a lot!