Dear all,
Can you explain me how to calculate sub net mask?
Thank!.:)
rch1231 169
Here is a subnet mask table that tells how many IP addresses are in a subnet based on the mask used:
ID # Bits Number Hosts Usable Hosts Netmask Note
6 /6 67108864 67108862 252.0.0.0
7 /7 33554432 33554430 254.0.0.0
8 /8 16777216 16777214 255.0.0.0 Class A Network
9 /9 8388608 8388606 255.128.0.0
10 /10 4194304 4194302 255.192.0.0
11 /11 2097152 2097150 255.224.0.0
12 /12 1048576 1048574 255.240.0.0
13 /13 524288 524286 255.248.0.0
14 /14 262144 262142 255.252.0.0
15 /15 131072 131070 255.254.0.0
16 /16 65536 65534 255.255.0.0 Class B Network
17 /17 32768 32766 255.255.128.0
18 /18 16384 16382 255.255.192.0
19 /19 8192 8190 255.255.224.0
20 /20 4096 4094 255.255.240.0
21 /21 2048 2046 255.255.248.0
22 /22 1024 1022 255.255.252.0
23 /23 512 510 255.255.254.0
24 /24 256 254 255.255.255.0 Class C Network
25 /25 128 126 255.255.255.128
26 /26 64 62 255.255.255.192
28 /28 16 14 255.255.255.240
27 /27 32 30 255.255.255.224
29 /29 8 6 255.255.255.248
30 /30 4 2 255.255.255.252
JorgeM 966
The subnet mask when applied to the IP address basically extracts the subnet portion of the IP address. This is done when you apply the AND operation against the IP address. What you do is convert the IP address into a binary number. Then you convert the subnet mask into a binary number. AND the numbers together, and the result is the subnet address.
Example:
IP: 1101 1000 . 0000 0011 . 1000 0000 . 0000 1100 (216.003.128.012)
Mask: 1111 1111 . 1111 1111 . 1111 1111 . 0000 0000 (255.255.255.000)
---------------------------------------------
1101 1000 . 0000 0011 . 1000 0000 . 0000 0000 (216.003.128.000)
