A .ip address basics

1.1 Structure and classification ip address

The tcp / ip protocol, each device connected to the internet must have a ip address, he is a 32-bit binary number, it may be expressed in dotted decimal, each of a set of eight, i.e., with a 0 to decimal notation 255, with each group. "" separated, e.g. 172.16.45.10

ip address indicates

After the ip address in the network and host bits fixed, ip address is divided into different accumulation: A Class, Classes B, Class C, Class D, E class

1.2 Special ip address

Network Address: is used to represent the network itself, with part of the normal network number and the host number part of all 0 ip address called a network address, such as the 172.16.45.0 network address is a class B
Broadcast address: for broadcast to all devices on the network. ip address having a network number of the normal portion and the main part of the whole number of 1 (i.e., 255) is referred to as a broadcast address, such as 172.16.45.255 is a class B network address
Limited broadcast address: refers to the full 32-bit bit 1 (i.e., 255.255.255.255) ip address, broadcast for this site
Loopback address: the network address can not begin as decimal 127, in the address number 127 is reserved for use as a diagnostic, called farewell address, such as 127.0.0.1 for loopback test
Private Address: can only be used in the LAN, ip address can not be used on the internet called private ip address private ip address are:
1. 10.0.0.0 ~ 10.255.255.255, a class A address represents
2. 172.16.0.0 ~ 172.31.255.255, Class B addresses 16 represents
3. 192.168.0.0 ~ 192.168.255.255, represents 256 Class C addresses
0.0.0.0: refers to the ip address is not in the true sense, it represents the all unknown host and the destination network, it is unclear here refers to no specific entry in the routing table indicates the machine how to reach

1.3 Subnet Mask

Subnet mask is used to identify the network address and host address ip address.
The subnet mask is 32-bit binary number in the subnet mask, the address corresponding to the part of the whole network is represented by 1, the host part of the whole is represented by 0
May also represent a subnet mask, i.e., "/ <digit network address>" with the network prefix, subnet mask as 172.16.45.0/24 of class B network 172.16.45.0 255.255.255.0

1.4 ip address of the applicant

https://www.processon.com/mindmap/57fdad47e4b08d4fe9b3d7e2

II. Subnetting

2.1 subnetting concept

Subnetting is to act as a subnet address of the host through a number of bits of the ip address borrowed bit original network thereby isolated from each other is divided into several sub-implemented

note:

arp protocol to obtain target host by ip address mac address of this process using a broadcast, the broadcast address is the address for the subnet by the subnet mask calculated from the hosts in the subnet only calculated in order to receive the broadcast packet arp
Subnetting can be done with the vlan isolate broadcast domains, subnetting is only three isolated, two two-story vlan

On the 2.2 c class subnetting

Subnetting step 2.3

To determine the number of hosts and subnets divided by the number of each subnet
Obtaining a corresponding number of subnets and N binary bits corresponding to the number of hosts binary number of bits M
Ip address of the original subnet mask, the N position thereof before the host address part 1 (all the rest set to 0) M 0 position (the rest are all set to 1) or after the subnet i.e. derived after the ip address subnetting mask

2.4 subnetting Case

A Class C network 211.168.10.0 subnet division 5

2-2 2 ** <5 <** 2 3-2 3 network number is needed, the host 8-3 = 5 Number

Subnet mask of 255.255.255.224

Each subnet can accommodate 5-2 = 2 ** 30 hosts

2.5 subnetting Notes

When subnetting need to consider not only current needs, future needs should also learn to say subnets and hosts. Subnet mask using the host bit more, get more subnets, the ip address resource conservation, if needed in the future more subnets, do not have to re-assign ip address, but a limited number of hosts per subnet; Conversely, fewer host subnet mask bits, each subnet hosts allows greater growth, but the limited number of available subnets
In general, too many nodes in a network, the network will broadcast communication because saturated, so the growth in the number of hosts in the network is limited, that is, under conditions permitting, should be more hosts bit for bit subnet

2.6 Why subnetting and its advantages

2.6.1 Why should subnetting:

Internet Organization defines five IP addresses for hosts are A, B, C three types of addresses. Wherein there are 126 class A network, each network may have a Class A 16,777,214 hosts, they are in the same broadcast domain. In the same broadcast domain there are so many nodes is not possible, because the network will broadcast communication and saturation, resulting in most of 16,777,214 addresses are not assigned to go out, forming a waste. On the other hand, as the Internet continues to expand applications, IP addresses fewer and fewer resources. In order to achieve a smaller broadcast domains and better utilization of every host address, it can be further divided into smaller network-based IP network class, defined by the router per subnet and subnet assigned a new network address, subnet address is created based on the host to borrow part of the network address class. After subnetting, by using a mask, the subnet hide, so that the network has not changed from the outside, this is the subnet mask.

It simply means that a company can not use the 254 public addresses, A company would like to use 6 addresses, B Company also want to use 6 addresses, if these two companies addresses are placed inside a large segment , the two companies will be able to directly address interoperability

2.6.2 subnetting advantage

Reduce network traffic
Improve network performance
Simplified management
Easy to expand the geographic scope

--- subnetting of network infrastructure