🌐 Subnet Reference Table

Bảng tham chiếu nhanh cho CIDR, Subnet Mask, Wildcard, và phân loại theo Class A/B/C/D.
Dữ liệu đầy đủ từ /0 đến /32 — tiện cho tra cứu khi học subnetting, network design, hoặc CCNA.

🧮 CIDR to Subnet Mask Reference

CIDRSubnet MaskHEX Mask# of IPsWildcard MaskHost BitsClass
/32255.255.255.255FF.FF.FF.FF10.0.0.00Single Host
/31255.255.255.254FF.FF.FF.FE20.0.0.111/1 C
/30255.255.255.252FF.FF.FF.FC40.0.0.321/2 C
/29255.255.255.248FF.FF.FF.F880.0.0.731/4 C
/28255.255.255.240FF.FF.FF.F0160.0.0.1541/8 C
/27255.255.255.224FF.FF.FF.E0320.0.0.3151/16 C
/26255.255.255.192FF.FF.FF.C0640.0.0.6361/32 C
/25255.255.255.128FF.FF.FF.801280.0.0.12771/64 C
/24255.255.255.0FF.FF.FF.002560.0.0.25581 C
/23255.255.254.0FF.FF.FE.005120.0.1.25592 C
/22255.255.252.0FF.FF.FC.001,0240.0.3.255104 C
/21255.255.248.0FF.FF.F8.002,0480.0.7.255118 C
/20255.255.240.0FF.FF.F0.004,0960.0.15.2551216 C
/19255.255.224.0FF.FF.E0.008,1920.0.31.2551332 C
/18255.255.192.0FF.FF.C0.0016,3840.0.63.2551464 C
/17255.255.128.0FF.FF.80.0032,7680.0.127.25515128 C
/16255.255.0.0FF.FF.00.0065,5360.0.255.255161 B
/15255.254.0.0FF.FE.00.00131,0720.1.255.255172 B
/14255.252.0.0FF.FC.00.00262,1440.3.255.255184 B
/13255.248.0.0FF.F8.00.00524,2880.7.255.255198 B
/12255.240.0.0FF.F0.00.001,048,5760.15.255.2552016 B
/11255.224.0.0FF.E0.00.002,097,1520.31.255.2552132 B
/10255.192.0.0FF.C0.00.004,194,3040.63.255.2552264 B
/9255.128.0.0FF.80.00.008,388,6080.127.255.25523128 B
/8255.0.0.0FF.00.00.0016,777,2160.255.255.255241 A
/7254.0.0.0FE.00.00.0033,554,4321.255.255.255252 A
/6252.0.0.0FC.00.00.0067,108,8643.255.255.255264 A
/5248.0.0.0F8.00.00.00134,217,7287.255.255.255278 A
/4240.0.0.0F0.00.00.00268,435,45615.255.255.2552816 A
/3224.0.0.0E0.00.00.00536,870,91231.255.255.2552932 A
/2192.0.0.0C0.00.00.001,073,741,82463.255.255.2553064 A
/1128.0.0.080.00.00.002,147,483,648127.255.255.25531128 A
/00.0.0.000.00.00.004,294,967,296255.255.255.25532Default Route

🅰️ Class A Subnetting

Network BitsSubnet Mask# of Subnets# of Hosts
/8255.0.0.0016,777,214
/9255.128.0.02 (0)8,388,606
/10255.192.0.04 (2)4,194,302
/11255.224.0.08 (6)2,097,150
/12255.240.0.016 (14)1,048,574
/13255.248.0.032 (30)524,286
/14255.252.0.064 (62)262,142
/15255.254.0.0128 (126)131,070
/16255.255.0.0256 (254)65,534
/17255.255.128.0512 (510)32,766
/18255.255.192.01024 (1022)16,382
/19255.255.224.02048 (2046)8,190
/20255.255.240.04096 (4094)4,094
/21255.255.248.08192 (8190)2,046
/22255.255.252.016384 (16382)1,022
/23255.255.254.032768 (32766)510
/24255.255.255.065536 (65534)254
/25255.255.255.128131072 (131070)126
/26255.255.255.192262144 (262142)62
/27255.255.255.224524288 (524286)30
/28255.255.255.2401048576 (1048574)14
/29255.255.255.2482097152 (2097150)6
/30255.255.255.2524194304 (4194302)2

🅱️ Class B Subnetting

Network BitsSubnet Mask# of Subnets# of Hosts
/16255.255.0.0065,534
/17255.255.128.02 (0)32,766
/18255.255.192.04 (2)16,382
/19255.255.224.08 (6)8,190
/20255.255.240.016 (14)4,094
/21255.255.248.032 (30)2,046
/22255.255.252.064 (62)1,022
/23255.255.254.0128 (126)510
/24255.255.255.0256 (254)254
/25255.255.255.128512 (510)126
/26255.255.255.1921024 (1022)62
/27255.255.255.2242048 (2046)30
/28255.255.255.2404096 (4094)14
/29255.255.255.2488192 (8190)6
/30255.255.255.25216384 (16382)2

🅲️ Class C Subnetting

Network BitsSubnet Mask# of Subnets# of Hosts
/24255.255.255.00254
/25255.255.255.1282 (0)126
/26255.255.255.1924 (2)62
/27255.255.255.2248 (6)30
/28255.255.255.24016 (14)14
/29255.255.255.24832 (30)6
/30255.255.255.25264 (62)2

🅳️ Class D (Supernets)

CIDR BlockSupernet Mask# of Class C# of Hosts
/14255.252.0.01024262,144
/15255.254.0.0512131,072
/16255.255.0.025665,536
/17255.255.128.012832,768
/18255.255.192.06416,384
/19255.255.224.0328,192
/20255.255.240.0164,096
/21255.255.248.082,048
/22255.255.252.041,024
/23255.255.254.02512