For this project we only use IPv4, so I won't talk about IPv6.
An IPv4-adress is a 32-bit number divided into 4 "blocks", each 8 bits.
i.e.:
192.168.100.1 turns into 11000000.10101000.01100100.00000001
So the min. value of one "block" is 0 and the max. value is 255.
The same logic applies to the network-mask:
255.255.255.0 turns into 11111111.11111111.11111111.00000000
Special to the mask is, after one bit was 0 there can't be any 1 bit's anymore.
So the only available numbers are:
255 (binary: 11111111)254 (binary: 11111110)252 (binary: 11111100)248 (binary: 11111000)240 (binary: 11110000)224 (binary: 11100000)192 (binary: 11000000)128 (binary: 10000000)0 (binary: 00000000)
Through which 255.255.255.0 is a valid mask
and 255.255.128.128 is not a valid mask.
In order to have the ability to send packages between two IP-addresses they either need to be part of the same network or they need to be connected by a router which is part of both subnets.
The following special address-ranges are reserved for Private Networks:
10.0.0.0 – 10.255.255.255
172.16.0.0 – 172.31.255.255
192.168.0.0 – 192.168.255.255
The following address-range is reserved for so called loopback addresses:
127.0.0.0 – 127.255.255.255
There is some more special ip-ranges, but for this project, you only need to remember those above.
The network-mask, subnet-mask or in our project only called mask is there to decide which range of ip-adresses are part of the same subnet.
There are 2 different ways of writing the mask:
- "Dot-decimal notation":
255.255.255.0 - "Class Inter-Domain Routing" or "CIDR":
/24
The more usable ip-addresses you need in one subnet, the less subnets you will be able to create.
To help you understanding it, I found this table very helpful:
| CIDR | Dot-decimal | Number of IP-addresses per subnet |
Usable IP-addresses per subnet |
Number of subnets |
|---|---|---|---|---|
| /32 | 255.255.255.255 | 1 | 0 | 256 |
| /31 | 255.255.255.254 | 2 | 0 | 128 |
| /30 | 255.255.255.252 | 4 | 2 | 64 |
| /29 | 255.255.255.248 | 8 | 6 | 32 |
| /28 | 255.255.255.240 | 16 | 14 | 16 |
| /27 | 255.255.255.224 | 32 | 30 | 8 |
| /26 | 255.255.255.192 | 64 | 62 | 4 |
| /25 | 255.255.255.128 | 128 | 126 | 2 |
| /24 | 255.255.255.0 | 256 | 254 | 1 |
The number of usable IP-addresses per subnet is lower than the total number of IP's because the first address is reserved as the network-address of the subnet and the last address is reserved as a broadcast-adress.
i.e. for mask 255.255.255.252:
network: 190.3.2.252
broadcast: 190.3.2.255
usable IP's: 190.3.2.253, 190.3.2.254
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Why does IPv4 need a netmask?
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Improved Network Security.
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Better Network Performance and Speed.
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Administration is a Breeze.
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Easier to Control Growth of Network.
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Less Network Congestion.
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A switch will enable you to connect more than two devices to the same network.
Its only purpose is to distribute packages to its network.
To see a working example, you can take a look at
(rule routers : control workflow between tasks in a process)
As previously mentioned a router is an interface which enables communication between different networks.
A router has the ability to be part of multiple networks, in Netpractice this is visualized by the so called Interface.
If routers and switches are still magic to you, I suggest looking deeper into it yourself, as their basic understanding is crucial to succeed in this project.
- Routing Table on Windows:
cmd on windows:
Get-NetRoute -AddressFamily IPv6
cmd on Mac:
netstat -rn
The routing table is there to store all the different paths to all the networks, the device is part of.
In Net_Practice the routing table consists of two elements, the destination and the next hop
The destination consists of the network-address that you want to send a package to, combined with the CIDR of that network: 190.3.2.252/30. If you don't want to specify a destination, you can just set it to default or 0.0.0.0/0.
The next hop is the address of the next router that you need to send the packages to in order to reach the destination-network.
And now to connect all of the above mentioned topics.
In order to have a functioning network, you now need to apply all of the parts talked about earlier.
If there should be a working connection in a network, the devices somehow need to be connected, either directly or with the help of routers which are part of both networks.
Now you may ask, how do I know if two devices are part of the same network?
For this you need to combine the IP-address and the mask of the devices in order to get the network-adress, that device is part of.
By combining I mean, doing a bit-by-bit-AND-opperation.
For that we first need to translate the IP and the mask to binary.
i.e.:
IP: 192.168.100.1 in binary: 11000000.10101000.1100100.00000001
MASK: 255.255.255.0 in binary: 11111111.11111111.11111111.00000000
Now you just combine the two bit by bit, if both bits are a 1 the corresponding bit of the network-address is 1, in any other case the corresponding bit is 0.
By doing that to the mentioned example, you should get the network-address of11000000.10101000.1100100.00000000 in binary or 192.168.100.0 in dot-decimal.
If two devices share the same network-address, they are part of the same network and communication is ensured.
Here are all the solutions and explanations for all 10 Levels.
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https://miro.com/app/board/uXjVMoh8dFU=/
https://www.youtube.com/watch?v=5WfiTHiU4x8&list=PLIhvC56v63IKrRHh3gvZZBAGvsvOhwrRF