Hi,
They would be in VLAN3. We came across minor issue using Hubs when we were waiting for data ports to be installed. We used a different VLAN for our printers so any printers that were in a hub that was also used for users had to have an address reserved from our user VLAN DHCP scope purely because the switch port connecting to the hub was in the user VLAN.
Also make sure that portfast is NOT enable on your switch ports connecting to the hub
Rgds
Paddy