How to determine subnets?

How to determine number of hosts and subnets?

• Hi all coulde kinda of an newbi qustione, But coulde any one step by step tell me this. Based on the IP network address 192.168.5.0/19. Determine the number of hosts and subnets if the required number of hosts are 5?

• Answer:

  Subnetting is pretty simple once you understand the back end. The slash notation is the number of bits being used by the subnet mask which determines your subnet. /19 could also be written as 255.255.224.0 or 11111111.11111111.11000000.00000000. Each octect is broken up into 8 bits. Each bit is a power of 2. Bit 1 = 2^7 = 128 Bit 2 = 2^6 = 64 Bit 3 = 2^5 = 32 Bit 4 = 2^4 = 16 Bit 5 = 2^3 = 8 Bit 6 = 2^2 = 4 Bit 7 = 2^1 = 2 Bit 8 = 2^0 = 1 Add all those values and get 256 which is maximum number any one octect can be (it is actually 255 but in binary we count 0 as a number). Now for the trick. If you write it out in binary draw a line where the 1s stop: 11111111.11111111.111|00000.00000000. Everything to the left is the network, everything to the right is the host. This leaves us with 13 bits for host values. This is where it all gets complicated. Here you have to determine how big each network is by determining the maxinum number of hosts per network and subtacting 2 (the first number in the host list as the network id and the last host as the broadcast address for the network). /19 leaves you 8 subnets and a total of 8190 hosts per subnet. Lets look at how many host you need. You said 5. You won't be able to do 5 naturally, so lets say 8 is the next number that is bigger than 5+2 (the plus two represents the network and broadcast addresses). We also know you are going to need a Class C subnet as your number of needed addresses is not more than 254. Give your self 5 extra bits on that Class C address of /24 and you get /29. 8192 Subnets and 6 hosts per subnet. Start with the address ranges to figure out your client count. 172.16.0.0 is our base, 255.255.255.248 is our mask. 172.16.0.0 - 172.16.07 = 8 hosts Subtract 2 hosts 172.16.0.1 - 172.16.0.6 = 6 usable hosts Just keep counting by 8 and you shoudl be able to figure it out. Sorry if this is kind of messy. This isnt' the best medium to describe this all.