IP address subnet determination

[MulliGan81]

Having an arbitrary public IP address is there a way to determine the subnet it belongs to whithout knowing the net-mask?

 

[Elizine]

You can't derive a specific net-mask with just the IP address. This IP could be a valid address in any number of sub-nets and could therefore have a number of net-masks. In addition, depending on the situation, a net-mask isn't necessarily static per address (i.e. more than one net-mask can be utilized for one address depending on the scenario and requirements).

 

[Mir96TA]

255.255.255.255 can be valid on any ip address

 

[drebo]

Search it on ARIN/RIPE/APNIC/whatever your local RIR is and it'll tell you which allocated block the IP is in.

Use a route server to see the actual advertised block it's part of.

That's the best you can do.