IP Terminology
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IP Terminology Bit-Like we talked about before is one digit, either a 1 or a 0 Byte- A byte is usually 8 bits, unless parity is used then it is 7 bits. Octet- Is usually in reference to 8 bits of an IP address A network address, such as 192.168.7.2 is much like a telephone number. With each octet( 192 and 168 in this IP address are each separate octets. ) representing another hierarchical level. If every computer on the Internet had its own unique IP address we would have run out of IP address along time ago. So they came up with a fix, NAT or Network Address Translation is used so that network users can use a private IP address on the network and then NAT will convert the address for use on the Internet. So lets talk about NAT for a moment. NAT translates private address to be used as global outside address. Take your network for example, instead of each computer having and IP address that allows it to access the Internet, NAT allows a network to only use one address to access the Internet. All routers look at the network as on IP address. Then the network routers break down the packets and deliver them to the appropriate address. There are several different types of NAT’s First you have the Static NAT. This allows one-one mapping between inside addresses and outside address. Dynamic NAT allows users to draw from a pool of address to go outside the network. Finally the most popular NAT is Overloading. Overloading or Port Address Translation allows the network users to connect to the Internet using only on IP address.
The network number is 170.70.0.0 and we are asked to use 1000 subnets in this scenario. 120, 121 and 122 are the subnets. We are asked to find the subnet addresses for the first two hosts and the last possible host for each number. Also we need to find the subnet mask for each. The subnet mask will be the same for each subnet. 1. First we need to figure out how many bits we will need to borrow to create a 1000 subnets. 1024 512 256 128 64 32 16 8 4 2 1 We will need to borrow 10 bits to create each network. To figure this out you add up each number 1, 2, 4, 8, 16…_ Until you get to 1000. Once you have gotten there, you stop. Under each number you put a 1, after you have gotten to 1000, add up all the 1s. You will get 10, therefore you have 10 bits. 2. We are in a class B network, which deals with the last two octets, we need to count over from the beginning of the second octet. 128 64 32 16 8 4 2 1 . 128 64 32 16 8 4 2 1 ** Counting over from the left 10 spaces you end at the asterisks. This is where you will do the calculating for you network numbers. Think of the asterisks as an imaginary line. 3. Count out the first network number 120, in bits. 1024 512 256 128 64 32 16 8 4 2 1 1 1 1 1 0 0 0 Remember the binary number 1111000 4. Insert the binary number 1111000 (that is the network number 120) into the two octets beginning at the right, but on the left of the asterisks. 128 64 32 16 8 4 2 1 . 128 64 32 16 8 4 2 1 1 1 1 1 0 0 0 ** _ 5. Add the numbers in each octet, you come up with 30 in the left octet and 0 in the right octet. This means that for your first network the IP address is 170.70.30.0 128 64 32 16 8 4 2 1 . 128 64 32 16 8 4 2 1 1 1 1 1 0 0 0 ** _ 6. Add 1 to the last octet for the first host and 2 to the last octet for your second host. IP Address- 170.70.30.1 Host 1- 170.70.30.1 Host 2-170.70.30.2 7. To figure out the last host, put 1s from the asterisks moving to the right, except under the 1 put a 0. This allows for a broadcast address. 128 64 32 16 8 4 2 1 . 128 64 32 16 8 4 2 1 —————————————————————————————————————————————————
Add these numbers up and that is your last possible host on the subnet. Last Host-170.70.30.62
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