Answer to Question #320499 in Computer Networks for bunny

Question #320499

Given following IP address 181.17.1.0/23; find subnet ID, network address, broadcast address and host address range?

Expert's answer

A 32-bit IP address uniquely identifies a single device on an IP network. The 32 binary bits are divided into the host and network sections by the subnet mask but they are also broken into four 8-bit octets.

Because binary is challenging, we convert each octet so they are expressed in dot decimal. This results in the characteristic dotted decimal format for IP addresses—for example, 172.16.254.1. The range of values in decimal is 0 to 255 because that represents 00000000 to 11111111 in binary.

IP Address Classes and Subnet Masks

Since the internet must accommodate networks of all sizes, an addressing scheme for a range of networks exists based on how the octets in an IP address are broken down. You can determine based on the three high-order or left-most bits in any given IP address which of the five different classes of networks, A to E, the address falls within.

(Class D networks are reserved for multicasting, and Class E networks not used on the internet because they are reserved for research by the Internet Engineering Task Force IETF.)

A Class A subnet mask reflects the network portion in the first octet and leaves octets 2, 3, and 4 for the network manager to divide into hosts and subnets as needed. Class A is for networks with more than 65,536 hosts.

A Class B subnet mask claims the first two octets for the network, leaving the remaining part of the address, the 16 bits of octets 3 and 4, for the subnet and host part. Class B is for networks with 256 to 65,534 hosts.

In a Class C subnet mask, the network portion is the first three octets with the hosts and subnets in just the remaining 8 bits of octet 4. Class C is for smaller networks with fewer than 254 hosts.

Class A, B, and C networks have natural masks, or default subnet masks: