netmask(1) - Linux man page
Jul 01, 2020 · It is called a subnet mask because it is used to identify network address of an IP address by perfoming a bitwise AND operation on the netmask. A Subnet mask is a 32-bit number that masks an IP address, and divides the IP address into network address and host address. A wildcard mask is a mask of bits that indicates which parts of an IP address are available for examination. In the Cisco IOS, they are used in several places, for example: . To indicate the size of a network or subnet for some routing protocols, such as OSPF. Jul 17, 2005 · In this case, the netmask of 255.255.255.248 represents 29 bits of network and 3 bits of host (totalling 32 bits, of course), and this give 8 possible IP addresses in this range. The first and last of the range are reserved addresses, giving 6 usable addresses that may be assigned to a device. May 14, 2019 · This wiki was founded on 11 October 2005. We have 3,125 articles.
You set the netmask with CIDR notation in the addresses, so /24 is 255.255.255.0, /25 is 255.255.255.128, /28 is 255.255.255.240, etc. Here is a working example from https://netplan.io/examples
Addresses Hosts Netmask Amount of a Class C /30: 4: 2: 255.255.255.252: 1/64 /29: 8: 6: 255.255.255.248: 1/32 /28: 16: 14: 255.255.255.240: 1/16 /27: 32: 30: 255.255 IP Calculator / IP Subnetting
We calculate the network size in "/16 networks" and use the second octett of the ip address and netmask. The size of the network is 16 /16 networks (the second octett runs from 16 to 31, giving 16 different values). The "interesting octett" in the netmask is now "256-16" (see above), so the netmask is 255.240.0.0.
Nov 17, 2017 · A subnet mask is the mean through which the host understands whether a packet is for this LAN or another one. In the latter case the packet is sent to a (default) gateway.