Which class of IPv4 addresses supports the largest number of host addresses in a computer network?
Class A
In classful IPv4 addressing, the 32-bit address is split into a network portion and a host portion. The number of hosts a single network can hold depends on how many bits are left for the host field: each network reserves two addresses (all-zero host bits = the network address, all-one host bits = the broadcast address), so usable hosts = 2h − 2, where h is the number of host bits.
The more host bits a class allocates, the larger the host capacity per network:
| Class | Network bits | Host bits | Usable hosts per network |
|---|---|---|---|
| A | 8 | 24 | 224 − 2 = 16,777,214 |
| B | 16 | 16 | 216 − 2 = 65,534 |
| C | 24 | 8 | 28 − 2 = 254 |
| D | Reserved for multicast — no host addressing | ||
Because Class A leaves the full 24 bits for hosts, it supports the largest number of host addresses per network — over 16 million. This is why Class A blocks were historically assigned only to very large organizations.
Class B, with 16 host bits, tops out at 65,534 hosts — large, but far below Class A. Class C offers only 254 hosts, suited to small networks. Class D is not a host-addressing class at all; its addresses (224.x.x.x–239.x.x.x) are reserved for multicast group delivery, so it cannot be the answer.
Important Questions from IPv4
A classless address is given as 167.199.170.82/27. The number of addresses in the network is
Which of the following class of IP address has the last address as 223.255.255.255?
What percentage (%) of the IPv4, IP address space do all class C addresses consume?
Consider the following two statements with respect to IPv4 in computer networking:
P: The loopback(IP) address is a member of class B network
Q: The loopback(IP) address is used to send a packet from host to itself
What can you say about the statements P and Q?
An Internet Service Provider (ISP) has the following chunk of CIDR-based IP addresses available with it: 245.248.128.0/20. The ISP wants to give half of this chunk of addresses to Organization A, and a quarter to Organization B, while retaining the remaining with itself. Which of the following is a valid allocation of addresses to A and B?
