IPv4 point to point addresses

In order to conserve IPv4 addresses, it is possible to use a /31 prefix for a point-to-point link. In such a case, such a subnet will have only two IP addresses, both of which will be used as host addresses. There are no network or broadcast addresses in such a scenario.

When such an address space is being advertised using a routing protocol, it is still the first address that is installed in the routing table. For example, for the subnet 192.168.14.2/31, there are two host addresses, specifically 192.168.14.2 and 192.168.14.3. Even so, if advertised by a routing protocol, 192.168.14.2/31 would appear in the routing table as the network address. The following is an example of a routing entry advertised via OSPF:

O 192.168.14.2/31 [110/2] via 192.168.12.1, 00:02:45, GigabitEthernet0/1

https://datatracker.ietf.org/doc/html/rfc3021