In classless interdomain routing (CIDR), the /32 subnet mask is one of the prefix lengths that is most confusing. Unlike the /31 subnet mask and other subnet masks we covered earlier, the /32 subnet mask does not divide a network into subnetworks; it rather defines the host route.
Once you assign an IP address to the interface of a network device (let’s say a router), the router will add two addresses to its routing table. The first is the network route, while the second is the host route. The network route is also called a connected route, and the host route is also called a local route.
For instance, if we have two network devices, Router A and Router B, connected over a point-to-point connection using the network 192.168.2.0/28.
IF we assign Router A the IP address 192.168.2.1 and Router B the IP address 192.168.2.2, Router A will add the host route (192.168.2.1/32) as well as the network route 192.168.2.0/28 to its routing table;
Router B will add the host route; 192.168.2.2/32 and network route; 192.168.2.0/28 to its routing table as well.
Note: A host route is a specific route to a destination (interface G0/0/0 of Routers A and B in this case).
/32 subnet mask dotted decimal
The dotted decimal for the /32 subnet mask is 255.255.255.255. This representation is obtained by setting the whole 32 bits of the IPV4 address to 1 and converting each octet to a decimal.
/32 Wildcard mask
The wildcard mask for the /32 prefix length is 0.0.0.0. This is obtained by subtracting each octet of the subnet mask from 255.
/32 Subnet Mask Usable IP Address.
In the /32 subnet mask, there is only one usable IP address, and this IP address is used to identify the host route. This one usable IP address can also be called a local route.
How Many Subnetworks are in /32?
A /32 subnet mask does not divide a network into subnetworks. It is rather used to define a route to a specific host in a network. Hence, there is no subnetwork in a /32 subnet mask.
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