How to Calculate Network and Broadcast Address

Step-by-Step Guide

1. 1

   Step 1: For a classful network total bits is 8.

   So Total bits = Tb =
   8.
   
   Sub-net mask can be 0, 128, 192, 224, 240, 248, 252, 254 and
   255.
   
   Below table gives you the "Number of bits used for subnetting"(n) to their corresponding subnet mask.
   
   For subnet mask 255 is default, so it'll not consider for subnet masking.
   
   For example:
   Let, IP address =
   210.1.1.100 and Sub-net mask =
   255.255.255.224 Total bits = Tb = 8 Number of bits used for subnetting = n = 3 (as subnet mask = 224 and its corresponding "No. of bits used for Subnetting" is 3 from above table)
2. 2

   Step 2: From the previous step

   Tb = m+n.
   
   Number of bits left for host = m = Tb
   - n = 8
   - 3 = 5 , Number of host per subnet = 2m
   -
   2.
   
   Number of subnets = 2n = 23 = 8 Value of last bit used for subnet masking = Δ = 2m = 25 = 32 , The 8 subnets (as calculated in previous step) are shown above.
   
   Each of them has 32 addresses. , Here the taken IP address is
   210.1.1.100 .
   210.1.1.100 comes in
   210.1.1.96
   -
   210.1.1.127 subnet (see the previous step table).
   
   So
   210.1.1.96 is network address and
   210.1.1.127 is broadcast address for the taken IP address i.e.
   210.1.1.100 .
3. 3

   Step 3: you got the "Number of bits used for subnetting"(n) and you know the "Tb"

4. 4

   Step 4: then you can get "Number of bits left for host"(m) = Tb - n as total bits is the summation of number of bits used for subnetting and number bits left for host i.e.

5. 5

   Step 5: Now you have to calculate "Number of subnets" = 2n and "Value of last bit used for subnet masking"(Δ) = 2m.

6. 6

   Step 6: Now you can find previously calculated number of subnets by separating subnets each having "Value of last bit used for subnet masking" or Δ addresses.

7. 7

   Step 7: Now you have to find that your IP address is in which subnet

8. 8

   Step 8: that subnet's first address is network address and last address is broadcast address.

Detailed Guide

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