The "smart wifi" upgrade will have no effect whatsoever if you have the Hub in modem mode and the Nighthawk doing all the heavy lifting. After all in modem mode - the SH2 is just that it has no routing or wifi capabilities.
If you are having issues with that sort of set up, then you should try setting it up again using the correct sequence (see below) , and if that doesnt sort it you may have a connection issue that we can help diagnose
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Set up your own router/Mesh unit (in its settings) with the WAN port set to be in Automatic IP i.e. DHCP (& Nat) mode, it may be pre-set that way anyway. Then, disconnect all cables from your new router (or Mesh first unit) and switch it off and unplug it.
Then, put the VM Hub into modem mode
(
https://www.virginmedia.com/help/virgin-media-hub-modem-mode )
and leave it 5-10' to initialise
Once it’s in modem mode, the VM hub “MUST” then be powered off. Switch your router on and make sure it’s fully initialised (leave 5 min) and then put in the ethernet cable from its WAN port to the VM hub (any port will do).
NOW… power up the VM hub and wait 5-10 minutes for The Hub to initialise and and you should get a stable connection. This order only needs to be done the first time you connect the router to the VM hub.
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John
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I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router +2 Airport Express's. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.