Dear Bitracer, thanks for your input
I did not meant 2 devices that are in the Guest Network, but devices/addresses that are in the “router’s” network, but not available to the Guest Wifi. Due to protection of the network, Guest Wifi does standard not allow Guest Wifi users to access devices in the network, logic.
but for certain devices like a printer it would be also logical that users can access those selected devices.
Some routers allow to add access permission to individual devices in a netwerk for Guest Wifi users, by configurating the permission to be accessed by the Guest network on the device/address level.