Trouble with 2.5gb, LAN works, internet doesnt

Hi guys, i have a hub 5 with a 2.5gb slot, i also have 4 computers (all ethernet cabled) all with 2.5gb nic cards, when i transfer files, the LAN is completely working fine, BUT i have no internet connection at all. Thats obviously when i have it plugged into the 2.5gb slot in hub.

If i put the cable into any other port on the hub, i have 1gb LAN and internet all around. (when the cable is connected to the hub 2.5gb, it goes into a 2.5gb switch, and the port colours all present the 2.5gb connections to the other 4 computers, so there is only one cable into my virgin 5 hub)

So, what am i doing wrong that i cant access internet if i use the 2.5gb port? That includes wifi. In fact, i cant even access 192.168.0.1 anymore unless i put the cable into one of the other 4 ports in virgin hub.

Can anyone advise please, i hope iv explained good enough, many thanks