The choice between using a /30 or /24 subnet mask for private networks is usually based on the specific network management and addressing need. Here are the main reasons to prefer /30 over /24 in certain contexts, especially when it comes to point-to-point links:

1. Efficiency in the Use of IP Addresses:

• final match.: Provides only 4 IP addresses, of which 2 are usable for the devices on the link. This is ideal for point-to-point links where you only need to connect two devices, such as links between routers or between a router and a switch in different locations. By using /30, you are optimizing the use of IP address space by not wasting unused addresses.
• final match.: Offers 256 IP addresses, with 254 usable for devices. Using /24 for a point-to-point link would waste a large number of IP addresses, which is neither practical nor efficient, especially in environments where IP address space is limited.

2. Simplicity and Clarity in Network Configuration:

• Using /30 on point-to-point links simplifies network configuration and makes it easier to understand network topology. Upon seeing a /30 subnet, network administrators can immediately assume that it is a point-to-point link without needing to investigate further.

3. Safety:

• By limiting the number of usable IP addresses on a subnet to just two, you reduce the scope for potential network attacks. There are no “extra” IP addresses on the subnet that could be exploited by unauthorized devices or malicious individuals. This helps strengthen the security of those specific links.

4. Configuration Error Prevention:

• Using /30 subnets for point-to-point links prevents the possibility of accidentally assigning IP addresses to unwanted devices. This can be particularly useful in large, complex networks, where IP address space management must be meticulous.

Additional considerations:

Although /30 has traditionally been preferred for point-to-point links for the reasons mentioned, it is important to mention that with the introduction of IPv6 and the wide availability of IP addresses, along with address preservation techniques such as NAT (Network Address Translation), some Some of these considerations may be less critical in modern environments.

Additionally, some networks may choose to use /31 for point-to-point links, a practice supported by more recent standards (RFC 3021) that allows two usable IP addresses without network or broadcast addresses, further maximizing address space efficiency in certain scenarios.