IP Routing Advanced Info

Howto by jmke @ 2003-01-23

This guide will be updated with more info now & then! Want to know what makes the internet work? Here you can find some info at least :)
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Advanced IP Routing Intro

Function of IP: To accept data from higher layer protocols TCP/UDP on a source host, create a datagram, and route the datagram through a network to a destination host.

The subnet mask specifies the portion of the IP address that is going to be used to define IP networks and subnetworks (as opposite to hosts).

The first bits of an IP address determine the address class:
* CLASS A : 1 byte for network - 3 bytes for hosts - RANGE: 1-127.x.x.x
* CLASS B : 2 bytes for network - 2 bytes for hosts - RANGE: 128-191.x.x.x
* CLASS C : 3 bytes for network - 1 byte for hosts - RANGE: 192-223.x.x.x
* CLASS D are multicast addresses used for sending a message to a specific group of hosts. They do not have a network and host number. RANGE: 224-239.x.x.x

Private Addressing used for Internal LAN´s (not published on the internet)
10.0.0.0 through 10.255.255.255
172.16.0.0 through 172.31.255.255
192.168.0.0 through 192.168.255.255

Example for a home LAN : CLASS C IP range (192.168.0.0/24)

192.168.0.0 -> Reserved for Network mask
192.168.0.255 -> Reserved Broadcast Address

IP address range: 192.168.0.1 -> 192.168.0.254
Subnet Mask: 255.255.255.0

192.168.0 (= network ID) .1 (= host id)

decimal vs binary presentation of an IP address:

192 . 168 . 0 . 1
1100 0000 . 1010 1000 . 0000 0000 . 0000 0001



Binary calculating:

0000 0000 = 0
0000 0001 = 1
0000 0010 = 2

Binary representation with decimal values <>:

11111111
1286432168421


Examples:

1111 1111 = 255
0001 1001 = 25

(more info on decimal/binary)
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