Discovering network subnets

[hannibal blog <hannibalsec () gmail com>]

hello list

I'm actually doing a blackbox audit of a network, and I'm trying to
discover network architecture.

I got this output with nmap X.X.X.0/24

interresting ports on X.X.X.0 
68/tcp
723/tcp
6000/tcp

I'm not sure the network is a C class one, but I'm surprised that such
an ip adress is an host IP.
What do u think ?
Any idea to guess network adressing map ?

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