Not as clear cut as that.
My DSL was in sync and was logged into internet but wouldn't resolve any web sites or ping any IP addresses. When I rebooted router, I then got sync but internet wouldn't authenticate.
It may have been that the DNS settings in the modem were using BT's DNS servers and the ones set on my modem are not responding. Maybe those using other DNS settings remain connected and working OK?
Zen Unlimited Fibre Office BQM