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Considering subnet masks, how many ways can 1 IPv4 address be interpreted?

T. Webster
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2 Answers2

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One IP address is one IP address. The subnet mask only defines how large the subnet around the address is (i.e. how many machines are on the LAN).

Netmask and hostmask are technically the same, only using a different notation. A netmask of 255.255.255.0 defines the same subnet as a hostmask of 0.0.0.255, which is the same as a prefix length of /24.

Sander Steffann
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Really you are asking how many different subnets might a given IP address belong to, if you don't know the subnet mask. This sounds an awful lot like a homework question.

Anyway, the smallest possible subnet is /32 with a subnet mask of 255.255.255.255. The largest possible subnet is /1 with a subnet mask of 128.0.0.0.

So there are 32 different possible subnet masks, but there are a different number of subnets possible for each mask. However, there are only a certain number of subnets for each size which a given IP address will be valid for. E.g. 1.2.3.4 is not a valid address in the subnet 254.254.254.0/24.

A further complexity will be whether you know that the IP address is assigned to a computer, and isn't therefore a subnet address or broadcast address, or one of the other restricted addresses - this would exclude some subnets that would otherwise be valid.

dunxd
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