8 end device limitation

Ref document

http://ftp1.digi.com/support/documentation/90000866_C.pdf
Page 28 section 4.2.1

I read in the ref. document a limit of 8 end device by routers.

Is my undestanding good? That means that if I have 10 end devices, i need at least 2 routers even if the end devices are very near?

I haven’t found this limitation anewhere in the ZigBee documentation. Is this something set by DIGI ?

This is a Digi set limitation. We have a certain amount of memory allocated for storing end device information. If more memory were allocated for a greater number of end devices, then that memory would have to be pulled from other features on the radio.

A coordinator can store up to 8 end devices as well. So if you have 10 sleeping end devices, then you would minimally need the coordinator and at least one additional router device.

Does the number of 8 based only on the available memory or is it an estimate threshold above what the performance will decrease? I think I ha ve read, but I can’t remember where, that above 8 children ZigBee begin to have performance issues.