(Note: NBN is fibre-to-the-premises broadband).
The devices shown in green work fine (can access the internal network as well as the Internet).
The device shown in red can't access either.
Can someone explain why this is so?
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Sign up to join this communityYour Internet access only provides access for one device. In this case, it's the router that's providing access to the other devices. The device in red has nothing to provide it with Internet access.
Generally speaking, the service provided by the vendor is plugged into a router. In some cases the service and router are in the same box, like a lot of cable providers do, but that doesn't appear to be the case here (I don't know what NBN equipment you have).
The normal way of setting this up is the NBN plugs into your router (WAN port), the switch into the router and then the rest of the devices into the switch. The reason for this is that you need a router in order for two different networks to talk to each other and your home network is different than the network coming from the NBN device.