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Software Engineering vocabulary · APIs, Networking and Security

Subnet mask

Meaning in software engineering, with examples

nounCore term

In software engineering, subnet mask means: A number such as 255.255.255.0 that shows which part of an IPv4 address identifies the network and which part identifies the device; it can also be written as a prefix such as /24.

In Turkish: alt ağ maskesi, subnet maskesi

How it is used

Entered together with the IP address and gateway, or handed out by DHCP. A wrong subnet mask is a classic configuration mistake: the device thinks local hosts are remote, or remote hosts are local. Engineers often just say 'the mask'.

Example sentences

  1. The server was set up with a /16 subnet mask instead of /24, so it couldn't reach the other offices.

  2. Check the subnet mask: 255.255.255.0 gives you 254 usable addresses.

Common collocations

  • wrong subnet mask
  • enter the subnet mask
  • /24 mask
  • mask and gateway
  • subnetA smaller range of IP addresses inside a larger network such as a VPC, used to group resources and control which of them can reach the internet.
  • CIDRShort for Classless Inter-Domain Routing: the system of writing an IP network as an address plus a prefix length, such as 192.168.0.0/22, which replaced the old fixed address classes.
  • IP addressA unique numerical label given to every device on an IP network so that data can be sent to it, for example 192.168.1.20 in IPv4.
  • default gatewayThe router address that a device sends traffic to when the destination is outside its own subnet; without it, a device can only talk to its local network.
  • IPv4Version 4 of the Internet Protocol, which uses 32-bit addresses written as four numbers from 0 to 255 separated by dots, such as 192.168.10.5; it allows about 4.3 billion addresses.

This word in other fields

The same English word can have a different meaning in another field:

More terms: APIs, Networking and Security

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