bima42/netpractice

NetPractice

Project made to learn basics of networking Pretty simple but you have to be confortable with some concept like IP address and mask

IP address

• allows elaboration and transport of IP datagrams (data packet) WITHOUT ENSURING THE DELIVERY
• process packets independently of each other by defining their representation, routing and forwarding

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Composed of 4 bytes, each composed of 8 bits

• a part reserved for the machine | part of the network
• Two IP addresses belong to the same subnet if they have the subnet mask bits in common.
• There are unavailable addresses:
  • From 10.0.0.0 to 10.255.255.255.
  • From 172.16.0.0 to 172.31.255.255
  • From 192.168.0.0 to 192.168.255.255 They are not unique: they are reserved for naming machines in a local network. Most of the time, the first machine connected to a Box will have the address 192.168.0.1. It is therefore not a routable address on the Internet at all.

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Mask

• Special feature: the masks include a sequence of bits of 1 then 0
• Number of machines that can be put on a network are defined by mask (right part or upper part)

Example :

• IP address: 192.168.0.0
• Subnet mask: 255.255.255.0
• Takes the upper part: image above, represents a byte which is 0. Can go from 0 to 255, or 256 numbers.
• Can code 256 addresses, but 2 addresses are reserved (0 and 255)
• 0: identifies the network (see image: 192.168.0.0)
• 255: broadcast address -> used to send a message to all network addresses (see image: 192.168.0.255)
• 256 - 2 = 254 usable addresses

CIDR

= Classless Inter-Domain Routing

• Another way to describe a mask
• gives the network number followed by a slash (or slash, “/”) and the number of bits at 1 in the binary notation of the subnet mask.
• /32 designates a network that has only one IP address, ie an individual IP address.
• Example: The mask 255.255.224.0, equivalent in binary to 11111111.11111111.11100000.00000000, will therefore be represented by /19 (19 bits at the value 1, followed by 13 bits 0).

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Routing

• network path selection mechanism for routing data from a sender to one or more recipients

Routing table

= data structure used by a router or networked computer

• associates prefixes with ways to route packets to their destination
• In NetPractice, the use of routes is mainly used to direct unwanted packets (default or 0.0.0.0/0) to the nearest interface. Or direct incoming packets from the internet to the nearest interface

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Example (Level 06)

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Sources

• Tuto : IP and Mask
• Route
• Calculator
• Other Calculator
• Routage