0 7 Net Bits 24 Host Bits example essay topic

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Ok, this explains sub net addressing which is useful if you run a scanner, a firewall, a router or anything else that is bound to IP sub net addressing. Note that this only describes IPv 4 sub nets. Reading binary values Normally, you read binary numbers byte wise (8 bit wise). Start at the last bit, bit 0.

If it is 1, add 2^0 to your number, else add 0. Then the next bit, bit 1, If it is 1, add 2^1 (2) to your number, If bit 3 is 1 add 2^2 (4) to your number, if bit 4 is 1 add 2^3 (8) to your number... if bit 8 is 1 add 2^7 (128) to your number. You see, the base is always 2 because it can be either 0 or 1. Now to sub net addressing. When you state a host including a sub net (example: n map), you do it like this: 1.2. 3.4/24, where /24 is the sub net.

Lets have a look at what this means: an IP address is a 32 bit address. 3.4'now, IP uses one part of this address to specify which Net it is on. Most of the time, this is a physical Net like an ethernet LAN that is linked to the internet. Nets that link to the internet get dedicated IPs for each of their hosts from the IANA. org. /24 means that the first 24 bits are the Net address and the remaining 8 bits are the Host address. SUBNET MASK: In this case, the sub net mask would be 255.255.

255.0. A sub net mask is created simply by filling all NET address bits with 1 and the HOST bits with 0. (11111111 = 255). There are 4 'Classes' on the Internet, which are the standard Subnets.

Class A: '0' + 7 net bits + 24 host bits, hosts 0.0. 0.0 to 126.255. 254 Class D: '1110' + 28 bits for multi cast addresses (reserved), hosts 224.0. 0.0 to 239.255.

255.254 Class E: '1111' + 28 bits for unused addresses ('martians'), hosts 240.0. 0.1 to 255.255. 255.254 0.0. 0.0/255.255. 255.255 = broadcast packets (0 and 255 are used for 'all hosts') One more example: If you address a sub net with the mask: 255.255.

192.0 (which is 111111111111111111 00000000000000), you can specify a sub net with: 190.136. 64.0/18 (18 net id bits) which would address 190.136. 64.0 to 190.136. 128.0 1011111010001000 10 00000000000000 190.136. 192.0 1011111010001000 11 00000000000000 Note: The first and the last sub net could not be used because Net ID 00 and 11 would be interpreted as broadcasts (like broadcast ids 0 (00000000) and 255 (11111111) ). For further info check the RFC 791 (web)..