IP address and subnet mask are two important concepts in computer networks. They jointly determine the address of a device in a local area network and the subnet to which the address belongs. Therefore, only the combination of the two can determine a unique address.
IP address is a unique digital label used to identify each device in a computer network. It allows data packets to be passed from one device to another in the network. IPv4 address consists of 32-bit binary numbers, usually divided into four 8-bit groups, each represented as a decimal number between 0 and 255.
Subnet mask is a 32-bit address mask used to determine whether the IP addresses of any two computers belong to the same subnet. In layman's terms, after the IP addresses of the two computers are ANDed with the subnet mask, if the results are the same, it means that these are two computers on the same subnet and can communicate directly.
Combination of IP address and subnet mask:
1. Determine the subnet range: The subnet mask and IP address are logically ANDed to obtain the network address. All IPs with the same network address belong to the same subnet. The subnet mask determines the number of hosts that can be divided and the number of subnets.
2. Routing selection: The router uses the subnet mask to determine whether the destination of the data packet is within the local subnet or in another subnet. If the destination IP address of the data packet matches the network address of one of the router's interfaces (compared by the subnet mask), the router knows that the data packet should be delivered within the local subnet. Otherwise, the router forwards the data packet to another subnet or network.
3. Avoid IP address conflicts: When configuring network devices, correctly setting the subnet mask can ensure that IP addresses do not conflict in different subnets.
4. CIDR (Classless Inter-Domain Routing): CIDR is a method of IP address allocation that relies on the subnet mask to determine the size of the network. CIDR makes the allocation of IP addresses more flexible and efficient.
Therefore, IP addresses and subnet masks are an indispensable part of network configuration. Together, they determine that devices in the network communicate with each other and that data packets are accurately delivered in the network.
