What are you connected to on the 6000, is it an M3, SUP-II, etc? And are you in the mgmt port? If you are in the mgmt port you will need to try 172.16.0.254 or change the mgmt interface IP.
If you are in a wired port, via one of the SFPs or a line card, make sure the ports are access in the vlan you configured, and that they are trusted.