The short answer: O2 Boost Boxes and Vodafone Sure signals don’t work on PPPoE connections (including Virgin Fibre and BT Infinity), due to a MTU (Maximum transmission unit) fault – they can’t handle anything less than 1500.
If you change broadband (It doesn’t specify how it detects the difference between dynamic IP broadband and switching broadband) then the box will be blacklisted “Locked” by O2 and requires a support call to unlock. You’ll need to do this once it’s connected to the final line.
O2 Boost Boxes and Vodafone Sure Signals are actually both Alcatel-Lucent Femtocell units.
When connected, they establish a ethernet connection, requesting an IP address via DHCP (this can be controlled using a static lease, NO CONTROL in box itself. MAC address of ethernet port on back of box
The box then established a connection using IPsec VPN, originating port 4500 UDP, and targetting port 4500. It can run inside a NAT, and doesn’t mind the port translation on the outside of the NAT router (apparent originating port will be some high number)
However, the IPsec connection WILL FAIL, if the MTU of any part of the connection is less than 1500. This means that the connection will work on “normal” ADSL connections using PPPoA. It won’t connect if you’re using PPPoE, such as BT Infinity (FTTC), as this has a MTU of 1492.
Once the box has connected via VPN, it connects to the provider (o2 or Vodafone), and retrieves it’s settings – you need to inform the provider of any mobile numbers you need the box to communicate with.