@Jabber 

When you are in the Guest network menu, where it says "Allow Guests To Access My Local Network:"

That should be set to Disabled, if it is, Enable it Save, switch it back to Disabled, and Save. The isolation option would prevent other devices connected to the Guest network from talking to each other, but should have no access to devices on the main network.

Thanks for getting back. Yes you would think so. Unfortunately, there is no such option.

Tough one! Any chance of a firmware fix? On the emulators for V1 V2 and V3 they have the option you mention. Not the V4. Running these in AP mode.

Thanks

@Jabber 

No, it doesn't have to do with the firmware. The reason you have access to the main network is becuase you are using the C50 in AP Mode. You need to set the router to be in router mode. 

In AP mode the router is just a passthrough device or a extension of the main router so the main router controls what packets go where. 

Great, bit pointless but looks like we'll be sending them back to the retailer.

Why wouldnt you want to run purely an AP for a wi-fi guest network?

Thanks anyway.

@Jabber 

You are very welcome