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Network Security Learning (XII) OSI and TCP

2022-07-25 22:52:00 【Shake light·】

Network topology

1. Star network topology , Double star network topology （ Most widely used in enterprises ）

High pressure at the central node （ Buy high-performance equipment ）

Easy to implement 、 Easy to expand the network 、 Easy troubleshooting

2. Network topology

High reliability

The cost is very high

TCP/IP Five layer protocol cluster / Protocol stack

application layer （DHCP,FTB,HTTP,RDP...) data

Transport layer （TCP/UDP） Data segment Process to process communication ( Port number )

The network layer （IP） message （ package ） Point to point communication

Data link layer frame

The physical layer The bit

The physical layer

1. Ethernet cable / Optical fiber

2. The bit

8bit=1Byte

1024B = 1KB

1024KB=1GB

1024GB=1TB

1024TB=1PB

3. The signal ：

Electrical signals ：

analog signal , digital signal （ Strong anti-interference ability , Short transmission ）

amplifier Repeater

optical signal ：

Fiber type ：

1） Single mode fiber （ Single light ） It's usually yellow

2） Multimode fiber It's usually orange / Blue

4. Ethernet cable / Twisted pair ：

5 Class a twisted pair

super 5 class

6 class

7 class

T568A： White and green , green , White orange , blue , White and blue , orange , White brown , Brown

T568B： White orange , orange , White and green , blue , White and blue , green , White brown , Brown

The use of cable classification ：

Cross line ： At one end A, At one end B. The same kind of equipment （ Equipment with more than three floors is regarded as the same kind of equipment ）

Through line ： It's on both ends A Or both B, Use between different kinds of equipment （ The Internet cables bought online are basically ）

All negative ： At one end A, At the other end is the opposite A, It is also known as console Line

Cisco software basic tutorial

console mouth , Used to open the switch management interface , Only enterprise switches

Ten trillion mouths （10Mb/s）

Ethernet

A hundred trillion mouths （100Mb/s）

Giga ports （1000Mb/s）

Ten thousand megabytes （10000Mb/s）

TengigabitEthernet（TE）

Most computers are adaptive gigabit network cards , Adaptive means that you can surf the Internet at a lower speed

Pictured , The computer works in 100m mode , The unit of Gigabit hour network speed is G

f0/1 analysis
f： A hundred trillion mouths
0： Module number
1： Interface number
0/1：0 The first interface on the module

Module installation

Because the router has only two network ports , Therefore, you need to install modules to contact the following figure PC

Double click to open the router interface —— There are optional modules on the left —— Shut down before installation

NM：network model Network module
2FE：2 individual FastEthernet mouth

After installation, there is a new port

Remove the router model

1. Open Settings

Uncheck the two items in the figure

Check the items in the figure

After modification, it is shown in the figure

Traffic grabber （wireshark）

One 、 network card

wireshark It is to crawl the data traffic on the host network card

1、 NIC mode

Hybrid mode ： No matter whether the goal is yourself , All received

Non hybrid model ： By default , The network card of the host is in this state , Will not accept non own data

2、 Interface understanding

3、 Two filters

Capture filter ： Filter before capturing packets

Display filter ： You can filter before and after capturing packets , But it will not affect the grabbed package （ Will grab all the bags , Only some packages are displayed when viewing ）

4、 filter

Capture filter

grammar

type ：host net port

Direction ：src dst

agreement ：ether ip tcp udp ftp..........

Logical operators ：&& And || or ！ Not

give an example

Grab source IP by 192.168.1.12 And the target port is 80 Message of