Tutorial 1:ip address and routing basic concepts

0. Description

Before learning the following content, there should be a basic understanding of TCP/IP, which we have mentioned many times before, it really does not involve the network data structure analysis, we only need in the heart of TCP/IP has the following concept:

TCP/IP Hierarchy	Focus
Application Layer	Various applications, such as Web applications, QQ, etc.
Transport Layer	Two kinds of connection protocols: TCP, UDP Transport Layer Port number
Network layer	IP address (used to find different networks)
Data Link Layer	MAC address (used to find different hosts in the LAN)
Physical Layer	Binary Data string

The content of this table is very important, it can be said that the TCP/IP protocol stack is very basic, so be sure to remember.

1. Review and introduction

As we said earlier, the router is a three-layer network device (the switch is a two-layer network device, the transponder is a physical layer network equipment), through the router, we can connect different networks (local area network), and these different LAN, there may be Ethernet, Token Ring network, and so on, as follows:

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(It is important to note that the structure of the token ring is certainly not the right one, just to make it easier to draw)

As shown in the figure above, it is through the use of routers, we can connect two different local area network, and the so-called different local area network, refers to the two local network host configuration IP address network number is not the same, about this concept, we will slowly mentioned below, now there is a recognition on it.

However, by 21st century today, the Token Ring network has been eliminated, and now we can see the vast majority of LAN types are Ethernet, so, in the absence of special instructions, we refer to the term "LAN" when referring to "Ethernet", so the above figure can be changed to the following:

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But now a question is, since are all Ethernet, then why say these two LAN is different LAN? Where the hell is that different? This is actually mentioned above, that is, the two local network host configuration IP address network number is not the same (now do not understand this sentence is not related, because there is no real start to speak IP address). Can understand: There are two people, they are people, but their identity is not the same, so we say this is two different people, but in essence they are people, the same reason, the so-called two different LAN, they are essentially local area network, but the identity of the two LAN is not the same.

For people, we can use name, ID number and so on as identity, then for the local area network, and what should be used as identity?

Ok! Perhaps you have guessed, is the IP address! One of the important functions of IP address is to distinguish between different local area networks, of course, it also has another function, that is to distinguish the same LAN in different host (PRO, a LAN can have a lot of hosts Ah, of course, to distinguish).

2.IP Address

(1) IP address and dotted decimal notation

The computer can know everything else is a binary number, so the actual IP address is a 32-bit binary number, just for us to look more easy to distinguish, we put it in decimal form, this method we call dotted decimal, as follows:

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Should be very good understanding, in fact, this point does not understand, is to examine your binary system in the end to learn. OK, if you feel understandable, try the following conversions:

binary IP address	dotted decimal notation
11000000|10100011|00000001|00000001
	10.10.120.16
01111111| 00000000|00000000|00000001

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Tutorial 1:ip address and routing basic concepts