[c-nsp] nhrp/dmvpn network-id

[danger will]

Hi there

i’ve been bashing my head around this problem for a few days please help 

ip nhrp network-id this is used to turn on nhrp on an interface and to 
provide the logical membership to a certain DMVPN cloud, otherwise 
stated each DMVPN cloud should have it’s unique network id, at least this is what all the design guides recommend.

What i did in my lab was to have each spoke and the hub in different 
DMVPN clouds meaning spoke one had network-id 1 , spoke 2 had network-id
 2, hub had network-id 3 etc and it seemed to work just fine so i don't 
understand the use of “ip nhrp network-id” and i can't seem to find a document to explain this in greater detail

Thanks