The Wildcard Mask
The wildcard mask is typically the inverse of the subnet mask configured on that interface. In a subnet mask, binary 1 is equal to a match and binary 0 is not a match. In a wildcard mask, the reverse is true, as shown in here:
- Wildcard mask bit 0 – Matches the corresponding bit value in the address.
- Wildcard mask bit 1 – Ignores the corresponding bit value in the address.
The easiest method for calculating a wildcard mask is to subtract the network subnet mask from 255.255.255.255, as shown for /24 and /26 subnet masks in the figure.
IPv4 Addresses and IPv4 Subnetting
| CIDR |
SUBNET MASK |
ADDRESSES |
WILDCARD MASK |
| /32 |
255.255.255. 255 |
1 |
0.0.0.0 |
| /31 |
255.255.255. 254 |
2 |
0.0.0.1 |
| /30 |
255.255.255. 252 |
4 |
0.0.0.3 |
| /29 |
255.255.255. 248 |
8 |
0.0.0.7 |
| /28 |
255.255.255. 240 |
16 |
0.0.0.15 |
| /27 |
255.255.255. 224 |
32 |
0.0.0.31 |
| /26 |
255.255.255. 192 |
64 |
0.0.0.63 |
| /25 |
255.255.255. 128 |
128 |
0.0.0.127 |
| /24 |
255.255.255.0 |
256 |
0.0.0.255 |
| /23 |
255.255.254.0 |
512 |
0.0.1.255 |
| /22 |
255.255.252.0 |
1024 |
0.0.3.255 |
| /21 |
255.255.248.0 |
2048 |
0.0.7.255 |
| /20 |
255.255.240.0 |
4096 |
0.0.15.255 |
| /19 |
255.255.224.0 |
8192 |
0.0.31.255 |
| /18 |
255.255.192.0 |
16384 |
0.0.63.255 |
| /17 |
255.255.128.0 |
32768 |
0.0.127.255 |
| /16 |
255.255.0.0 |
65536 |
0.0.255.255 |
| /15 |
255.254.0.0 |
131072 |
0.1.255.255 |
| /14 |
255.252.0.0 |
262144 |
0.3.255.255 |
| /13 |
255.248.0.0 |
524288 |
0.7.255.255 |
| /12 |
255.240.0.0 |
1048576 |
0.15.255.255 |
| /11 |
255.224.0.0 |
2097152 |
0.31.255.255 |
| /10 |
255.192.0.0 |
4194304 |
0.63.255.255 |
| /9 |
255.128.0.0 |
8388608 |
0.127.255.255 |
| /8 |
255.0.0.0 |
16777216 |
0.255.255.255 |
| /7 |
254.0.0.0 |
33554432 |
1 .255.255.255 |
| /6 |
252.0.0.0 |
67108864 |
3 .255.255.255 |
| /5 |
248.0.0.0 |
134217728 |
7 .255.255.255 |
| /4 |
240.0.0.0 |
268435456 |
15. 255.255.255 |
| /3 |
224.0.0.0 |
536870912 |
31. 255.255.255 |
| /2 |
192.0.0.0 |
1073741824 |
63. 255.255.255 |
| /1 |
128.0.0.0 |
2147483648 |
127. 255.255.255 |
| /0 |
0.0.0.0 |
4294967296 |
255. 255.255.255 |
| Classful IPv4 Addresses |
| Class A |
0.0.0.0 – 127.255.255.255 |
| Class B |
128.0.0.0 – 191.255.255.255 |
| Class C |
192.0.0.0 – 223.255.255.255 |
| Class D |
224.0.0.0 – 239.255.255.255 |
| Class E |
240.0.0.0 – 255.255.255.255 |
| Private IPv4 Addresses |
| 10.0.0.0 – 10.255.255.255 |
| 172.16.0.0 – 172.31.255.255 |
| 192.168.0.0 – 192.168.255.255 |
| Special IPv4 Addresses |
| Local Host |
127.0.0.0 – 127.255.255.255 |
| APIPA |
169.254.0.0 – 169.254.255.255 |
| Bogon IPv4 Addresses |
| 0.0.0.0/8 |
This network |
| 10.0.0.0/8 |
Private IPv4 Address Block |
| 100.64.0.0/10 |
Carrier-grade NAT |
| 127.0.0.0/8 |
Loopback |
| 127.0.53.53 |
Name collision occurrence |
| 169.254.0.0/16 |
Link local |
| 172.16.0.0/12 |
Private IPv4 Address Block |
| 192.0.0.0/24 |
IETF protocol assignments |
| 192.0.2.0/24 |
TEST-NET-1 |
| 192.168.0.0/16 |
Private IPv4 Address Block |
| 198.18.0.0/15 |
Network benchmark testing |
| 198.51.100.0/24 |
TEST-NET-2 |
| 203.0.113.0/24 |
TEST-NET-3 |
| 224.0.0.0/4 |
Multicast |
| 240.0.0.0/4 |
Reserved |
| 255.255.255.255/32 |
Limited broadcast |
Lovely!
A lot thanks!