Network Quick Reference

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Class Quick Reference

Class Leading Bits Start End # of Networks Default Mask CIDR
A 0 0.0.0.0 127.255.255.255 128 (27) 255.0.0.0 /8
B 10 128.0.0.0 191.255.255.255 16384 (214) 255.255.0.0 /16
C 110 192.0.0.0 223.255.255.255 2097152 (221) 255.255.255.0 /24
D (multicast) 1110 224.0.0.0 239.255.255.255 undef undef undef
E (reserved) 1111 240.0.0.0 255.255.255.255 undef undef undef

Netmask Quick Reference

# Bits # Hosts Usable Hosts Netmask Cisco Mask
/4 268435456 (221) 268435454 240.0.0.0 15.255.255.255
/5 134217728 (221) 134217726 248.0.0.0 7.255.255.255
/6 67108864 (221) 67108862 252.0.0.0 3.255.255.255
/7 33554432 (221) 33554430 254.0.0.0 1.255.255.255
/8 16777216 (224) 16777214 255.0.0.0 class A network 0.255.255.255
/9 8388608 (223) 8388606 255.128.0.0 0.127.255.255
/10 4194304 (222) 4194302 255.192.0.0 0.63.255.255
/11 2097152 (221) 2097150 255.224.0.0 0.31.255.255
/12 1048576 (220) 1048574 255.240.0.0 0.15.255.255
/13 524288 (219) 524286 255.248.0.0 0.7.255.255
/14 262144 (218) 262142 255.252.0.0 0.3.255.255
/15 131072 (217) 131070 255.254.0.0 0.1.255.255
/16 65536 (216) 65534 255.255.0.0 class B network 0.0.255.255
/17 32768 (215) 32766 255.255.128.0 0.0.127.255
/18 16384 (214) 16382 255.255.192.0 0.0.63.255
/19 8192 (213) 8190 255.255.224.0 0.0.31.255
/20 4096 (212) 4094 255.255.240.0 0.0.15.255
/21 2048 (211) 2046 255.255.248.0 0.0.7.255
/22 1024 (210) 1022 255.255.252.0 0.0.3.255
/23 512 (29) 510 255.255.254.0 0.0.1.255
/24 256 (28) 254 255.255.255.0 class C network 0.0.0.255
/25 128 (27) 126 255.255.255.128 0.0.0.127
/26 64 (26) 62 255.255.255.192 0.0.0.63
/27 32 (25) 30 255.255.255.224 0.0.0.31
/28 16 (24) 14 255.255.255.240 0.0.0.15
/29 8 (23) 6 255.255.255.248 0.0.0.7
/30 4 (22) 2 255.255.255.252 0.0.0.3
/31 2 (21) point to point links only
/32 1 (20) 1 255.255.255.255 single IP address use host notation