How to calculate the IP range when the IP address and the netmask is given

Question

When a IP-Range is written as aaa bbb ccc ddd netmask  CIDR Notation  I need to calculate the first and the last included ip address in this range with C    Example   Input  192 168 0 1 25  Result  192 168 0 1 - 192 168 0 126

User · Answer

I learned this shortcut from working at the network deployment position. It helped me so much, I figured I will share this secret with everyone. So far, I have not able to find an easier way online that I know of.

For example a network 192.115.103.64 /27, what is the range?

just remember that subnet mask is 0, 128, 192, 224, 240, 248, 252, 254, 255

255.255.255.255 11111111.11111111.11111111.11111111 /32

255.255.255.254 11111111.11111111.11111111.11111110 /31

255.255.255.252 11111111.11111111.11111111.11111100 /30

255.255.255.248 11111111.11111111.11111111.11111000 /29

255.255.255.240 11111111.11111111.11111111.11110000 /28

255.255.255.224 11111111.11111111.11111111.11100000 /27

255.255.255.192 11111111.11111111.11111111.11000000 /26

255.255.255.128 11111111.11111111.11111111.10000000 /25

255.255.255.0 11111111.11111111.11111111.00000000 /24

from /27 we know that (11111111.11111111.11111111.11100000). Counting from the left, it is the third number from the last octet, which equal 255.255.255.224 subnet mask. (Don't count 0, 0 is /24) so 128, 192, 224..etc

Here where the math comes in:

use the subnet mask - subnet mask of the previous listed subnet mask in this case 224-192=32

We know 192.115.103.64 is the network: 64 + 32 = 96 (the next network for /27)

which means we have .0 .32. 64. 96. 128. 160. 192. 224. (Can't use 256 because it is .255)

Here is the range 64 -- 96.

network is 64.

first host is 65.(first network +1)

Last host is 94. (broadcast -1)

broadcast is 95. (last network -1)

User · Answer

I know this is an older question  but I found this nifty library on nuget that seems to do just the trick for me   http   nuget org packages TakeIo NetworkAddress

User · Answer

Invert mask  XOR with ones   AND it with IP  Add 1  This will be the starting range  OR IP with mask  This will be the ending range

User · Answer

my good friend Alessandro have a nice post regarding bit operators in C   you should read about it so you know what to do  It s pretty easy  If you break down the IP given to you to binary  the network address is the ip address where all of the host bits  the 0 s in the subnet mask  are 0 and the last address  the broadcast address  is where all the host bits are 1  For example  ip 192 168 33 72 mask 255 255 255 192  11111111 11111111 11111111 11000000  subnet mask  11000000 10101000 00100001 01001000  ip address   The bolded parts is the HOST bits  the rest are network bits   If you turn all the host bits to 0 on the IP  you get the first possible IP  11000000 10101000 00100001 01000000  192 168 33 64   If you turn all the host bits to 1 s  then you get the last possible IP  aka the broadcast address   11000000 10101000 00100001 01111111  192 168 33 127   So for my example  the network is  quot 192 168 33 64 26 quot   Network address  192 168 33 64 First usable  192 168 33 65  you can use the network address  but generally this is considered bad practice  Last useable  192 168 33 126 Broadcast address  192 168 33 127

User · Answer

You might already know this  but to check that you re getting this stuff right have a look at http   www subnet-calculator com  - you can see there how the bits represent the network and host portions of the address

User · Answer

I would recommend the use of IPNetwork Library https   github com lduchosal ipnetwork  As of version 2  it supports IPv4 and IPv6 as well   IPv4    IPNetwork ipnetwork   IPNetwork Parse  192 168 0 1 25       Console WriteLine  Network    0    ipnetwork Network     Console WriteLine  Netmask    0    ipnetwork Netmask     Console WriteLine  Broadcast    0    ipnetwork Broadcast     Console WriteLine  FirstUsable    0    ipnetwork FirstUsable     Console WriteLine  LastUsable    0    ipnetwork LastUsable     Console WriteLine  Usable    0    ipnetwork Usable     Console WriteLine  Cidr    0    ipnetwork Cidr     Output    Network   192 168 0 0   Netmask   255 255 255 128   Broadcast   192 168 0 127   FirstUsable   192 168 0 1   LastUsable   192 168 0 126   Usable   126   Cidr   25   Have fun

User · Answer

Input  192 168 0 1 25  The mask is this part   25  To find the network address do the following    Subtract the mask from the ip length  32 - mask    32 - 25   7 and take those bits from the right In the given ip address  I e  192 168 0 1 in binary is  11111111   11111111  00000000  00000001 Now  taking 7 bits from right  0  1111111   11111111  00000000  00000000 Which in decimal is  192 168 0 0  this is the network address     To find first valid usable ip address add  1 to network address I e  192 168 0 1  To find the last broadcast address the procedure is same as that of finding network address but here you have to make   32-mask  bits from right to  1   I e  11111111   11111111  00000000  01111111 Which in decimal is 192 168 0 127  To find the last valid usable ip address subtract 1 from the broadcast address  I e  192 168 0 126

User · Answer

I ll just post the code   IPAddress ip   new IPAddress new byte     192  168  0  1     int bits   25   uint mask     uint MaxValue  gt  gt  bits       Convert the IP address to bytes  byte   ipBytes   ip GetAddressBytes        BitConverter gives bytes in opposite order to GetAddressBytes    byte   maskBytes   BitConverter GetBytes mask  Reverse   ToArray     byte   startIPBytes   new byte ipBytes Length   byte   endIPBytes   new byte ipBytes Length       Calculate the bytes of the start and end IP addresses  for  int i   0  i  lt  ipBytes Length  i          startIPBytes i     byte  ipBytes i   amp  maskBytes i        endIPBytes i     byte  ipBytes i     maskBytes i          Convert the bytes to IP addresses  IPAddress startIP   new IPAddress startIPBytes   IPAddress endIP   new IPAddress endIPBytes

[c#] How to calculate the IP range when the IP address and the netmask is given?

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