Zigbee mesh question

[upbeat pilot]

From my understanding, zigbee devices create a mesh network. The coordinator (in my case, HA with a ZBdongle-e) needs to pair with the device initially, but can rely on other devices to pass data back and forth.

I have 2 SNZB-02D sensors, one on the top floor landing, and another in the bedroom. The top floor sensor is feeding data back to HA, but the bedroom one isn't. The top floor one is about 5 meters away from the bedroom sensor and has line of sight to it.

If zigbee creates a mesh, doesn't this mean the top floor sensor should be able to relay data for the bedroom sensor back to my HA?

[unkempt needle]

No, because it's battery powered. Only devices plugged into the wall will act as routers, and there are some mains powered devices that still won't act as a router (you'd need to see their documentation to know).

The easiest way to extend the mesh is to add a Zigbee plug and then pair the distant sensor to it. It will then relay the messages to the coordinator

Point is, only devices that are designed to be routers extend the mesh, and no battery powered devices are routers because they sleep most of the time