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IPv4 Subnet Mask Table

One A4 page: every IPv4 prefix, mask, wildcard, address count, subnet boundaries and special-range reminders.

For the calculation steps, read the subnetting worked examples. To calculate a particular address, use the IPv4 subnet calculator.

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IPv4 Subnet Mask TablePJH-Tech / FIELD REFERENCE
CIDRSubnet maskWildcardAddressesUsable hosts*
/00.0.0.0255.255.255.2554,294,967,2964,294,967,294
/1128.0.0.0127.255.255.2552,147,483,6482,147,483,646
/2192.0.0.063.255.255.2551,073,741,8241,073,741,822
/3224.0.0.031.255.255.255536,870,912536,870,910
/4240.0.0.015.255.255.255268,435,456268,435,454
/5248.0.0.07.255.255.255134,217,728134,217,726
/6252.0.0.03.255.255.25567,108,86467,108,862
/7254.0.0.01.255.255.25533,554,43233,554,430
/8255.0.0.00.255.255.25516,777,21616,777,214
/9255.128.0.00.127.255.2558,388,6088,388,606
/10255.192.0.00.63.255.2554,194,3044,194,302
/11255.224.0.00.31.255.2552,097,1522,097,150
/12255.240.0.00.15.255.2551,048,5761,048,574
/13255.248.0.00.7.255.255524,288524,286
/14255.252.0.00.3.255.255262,144262,142
/15255.254.0.00.1.255.255131,072131,070
/16255.255.0.00.0.255.25565,53665,534
/17255.255.128.00.0.127.25532,76832,766
/18255.255.192.00.0.63.25516,38416,382
/19255.255.224.00.0.31.2558,1928,190
/20255.255.240.00.0.15.2554,0964,094
/21255.255.248.00.0.7.2552,0482,046
/22255.255.252.00.0.3.2551,0241,022
/23255.255.254.00.0.1.255512510
/24255.255.255.00.0.0.255256254
/25255.255.255.1280.0.0.127128126
/26255.255.255.1920.0.0.636462
/27255.255.255.2240.0.0.313230
/28255.255.255.2400.0.0.151614
/29255.255.255.2480.0.0.786
/30255.255.255.2520.0.0.342
/31255.255.255.2540.0.0.122 endpoints*
/32255.255.255.2550.0.0.011 host*

Find the boundary

Network = IP AND mask. Broadcast = network OR wildcard. Block increment in the partial octet = 256 − mask octet. A /27 steps by 32: .0, .32, .64, .96, .128, .160, .192, .224.

10.42.31.173/27 → network .160, broadcast .191, hosts .161–.190 (30).

Keep these distinctions

RFC 1918: 10/8, 172.16/12, 192.168/16.
CGNAT: 100.64/10 is shared space, not RFC 1918.
Link-local: 169.254/16 stays on the link.

* Ordinary hosts = addresses − 2. /31 uses both endpoints on point-to-point links; /32 is a host route. Special-use blocks are not all assignable.

Powers: 2⁰=1 · 2¹=2 · 2²=4 · 2³=8 · 2⁴=16 · 2⁵=32 · 2⁶=64 · 2⁷=128 · 2⁸=256 · 2¹⁰=1,024

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References