Using a Sagemcom F@ST 3864 router connected via cable. WiFi works fine but none of the lan connections. Had the same issue a few months ago. Occurred completely randomly (no changes at my end) and tried hard resets, disconnecting and reconnecting etc. This eventually worked last time but has happened again and doesnt seem to work. I gathe rthis is a know issue
I've seen something similar from 2 other people on here in the last 2-3 months and while 3 people out of the 1000's of customers Optus has doesn't necessarily indicate a trend, it could be the beginning of one. I'd say the modem is faulty so you're best to call support and have them troubleshoot and send a new one.