If using the
Superhub in modem mode, only one port on the superhub is active and that is the only one that can be connected to the WAN port of your router. I believe you must use port 1, closest to the cable connection.
I would set the superhub to modem mode and then let it power down. Make sure the router is also powered down (if you have any doubt on what the router's settings are do a factory reset on that too). Now connect your superhub to the router. Only then should you power up the superhub in modem mode and let that settle down and wait for it, then power up the router.
But a quick google shows vyatta is a software based router system you have presumably installed onto a computer? If so, do you know if you have that configured correctly? To prove to yourself the superhub is working fine in modem mode, follow the setup procedure I outlined above but substitute a working ethernet wired based computer instead of the router and you should see the computer get a connection to the modem mode superhub and thus internet.