Pairing Zigbee devices

[BuddyCasino]

I'm looking at my ESP32C6 that I ordered, and the Zigbee code samples. It seems the network ID is hardcoded in those samples. How is joining an existing Zigbee network usually done? Is this something that is doable with the C6 hardware, or does this require something external like NFC, considering that n the case of the Ikea switches, one has to move two devices close to each other for a few seconds. Is knowing the network ID enough, or are additionally cryptographic keys required?