What a /14 subnet is: a four-way /16 aggregate
A /14 holds 262,144 addresses, exactly four contiguous /16 networks. It shows up as a route summary rather than as a subnet anyone assigns to an interface.
At a glance
- Subnet mask
- 255.252.0.0
- Wildcard mask
- 0.3.255.255
- Total addresses
- 262,144
- Usable hosts
- 262,142
- Contains
- 1,024 networks of /24
- Host bits
- 18 of 32
In detail
The mask is 255.252.0.0. The value of the second octet must be a multiple of four for the network address to be valid, which is the arithmetic that makes summarisation work.
Route summarisation is the reason to care: advertising 10.4.0.0/14 instead of four separate /16s cuts the routing table and hides a change inside one of them from the rest of the network.
When you summarise, check that you own every address inside the summary. Advertising a /14 that includes a /16 you do not control creates a black hole for that /16.
Examples
10.4.0.0/16
10.5.0.0/16
10.6.0.0/16
10.7.0.0/16
# summarise to one route
10.4.0.0/14 covers 10.4.0.0 to 10.7.255.255Things that catch people out
- 10.5.0.0/14 is not a valid network address. The second octet must be divisible by 4, so the block starting near it is 10.4.0.0/14.
- Summarising across a discontiguous allocation advertises addresses you do not have, and traffic for them arrives and is dropped.
Try it: IP Subnet Calculator
Enter any IPv4 address with a prefix or a dotted mask and get the network address, broadcast address, wildcard mask, usable host range, address class, and the hex and binary forms.
IP Subnet Calculator
LOCAL · Browser-OnlyCalculate IP subnet details, network ranges, and CIDR notation
192.168.1.0192.168.1.255255.255.255.00.0.0.255192.168.1.0/24192.168.1.1 - 192.168.1.254192.168.1.1192.168.1.254256254C0xC0A8016411000000.10101000.00000001.01100100Split into two /25 subnets
Dividing 192.168.1.0/24 one prefix deeper.
Common Subnet Masks
Related IPv4 subnets
All ipv4 subnets →What a /16 subnet is: a full class B block
A /16 uses the mask 255.255.0.0 and gives 65,534 usable addresses. What it is for and where it goes wrong.
What a /12 subnet is: the 172.16 private block
A /12 uses the mask 255.240.0.0 and gives 1,048,574 usable addresses. What it is for and where it goes wrong.
What a /22 subnet is: four /24s
A /22 uses the mask 255.255.252.0 and gives 1,022 usable addresses. What it is for and where it goes wrong.
What a /18 subnet is: a quarter of a /16
A /18 uses the mask 255.255.192.0 and gives 16,382 usable addresses. What it is for and where it goes wrong.
What a /20 subnet is: sixteen /24s
A /20 uses the mask 255.255.240.0 and gives 4,094 usable addresses. What it is for and where it goes wrong.
What a /21 subnet is: eight /24s
A /21 uses the mask 255.255.248.0 and gives 2,046 usable addresses. What it is for and where it goes wrong.
Tools for this
- IP Subnet Calculator Free online IP subnet calculator - calculate IP subnet details, CIDR notation, and network address ranges
- IP Address Lookup Free online IP address lookup - find your public IP address and basic network information
- Number Base Converter Free online number base converter - convert numbers between decimal, binary, octal, and hexadecimal