20150908 Linux operation and Maintenance Network Foundation and TCP finite state machine state transition principle, Linux network attribute configuration and network

1, the network of O Internet model

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Physical layer: Electrical signals, network cards, bit streams, data-end devices provide data transfer

Data Link layer: Transfers data from the network layer to the neighboring destination network layer. IP messages,

Network layer: Responsible for providing communication services to different hosts on the packet switch, TCP/IP layer (implemented in Linux kernel)

Transport Layer: Two hosts inter-process Communication service, through the form of port (random port) is the source of communication

Application tiers: Services directly to users ' applications (implemented in customer applications) such as: HTTP, Tomcat

Osi	Data transfer format	Agreement
Session, presentation, application layer	Message	HTTP FTP SMTP
Transport Layer	tcp/Data Segment udp/packet	TCP UDP
Network layer	Grouping (package), grouping size varies by protocol	ICMP IGMP RARP ARP
Data Link Layer	Frames, one frame, multiple bit streams	Various network interfaces
Physical Layer	Bit stream

2. The principle of peer session for network architecture

Network communication must be established at the peer level of the communication between the two sides, can not be staggered

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Transport layer communication using a random port greater than 1024

3, the TCP model in the transport layer of the two transport Protocol differences

TCP (Transport Management Protocol) UDP (User Datagram Protocol)

Project	Tcp	Udp
Whether to connect	Connection-oriented (three-time handshake)	For non-connected
Transmission Reliability	Reliable	Unreliable
Application situations	Transmission of large quantities	Small amount of data
Speed	Slow	Fast

4. Three handshake and disconnection of TCP protocol

First communication three-time handshake TCP has a connection process, customer request SYN,

The server returns a request (Ack received), and the server is returned to the client,

The client sends an ACK message to determine the relevant content for communication.

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Four-time disconnection:

The client sends a disconnect request,

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The difference between a three-time handshake and a four-break is to ensure no data transfer

The process is as follows:

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5, Flow cleaning

The service is generally provided by the operator, and at the exit there is a splitter that imports all the traffic mirror images into

Intrusion detection on professional equipment, access control rules (Intelligent learning function). When the study is complete

After opening, this time all the traffic is not imported into the spectrometer, directly into the device. And the back end of that device

Once cleaned and then back to the server. The previous configuration information is retained. Not proofread will give up! Incoming traffic

is normal flow (will release, abnormal will give up)

Intelligent Learning Library running in memory

6. Linux Network Configuration

A:ifconfig Definition Description

Linux network address on the kernel

Ifconfig

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ENS33 for local network card, Lo local loopback: test use

ScopeID function range, valid for current NIC

MTU Network Maximum Transmission Unit

Rx/tx Receiving and contracting the package

Dropped occurs when IO is high

Overruns refers to overload (exceeding NIC Buffer)

B: Command format

NAME

Ifconfig-configure a network interface

Synopsis

Ifconfig [-v] [-a] [-s] [interface]

Ifconfig [-v] interface [Aftype] options | Address ...

NOTE

This program is obsolete! For replacement check IP addr and IP link. For statistics use Ip-s link.

Ifup command to enable a network card

Ifconfig network card device supports long format and short format

For example 255.255.255.0 for long format IP address/24 24 for short format

The general order is temporary and effective, long-term effective need to modify the file

Configure aliases

Ifconfig ens33:1 172.16.16.106/24

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Ens33:1 as Alias

Linux network address is kernel level

C: Routing Configuration

Default gateway required for configuring routing by default (gateway)

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Route display routes Route-n in digital display

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Route add 172.16.16.105 GW plus gateway specifies the NIC to upload to a network card

Type

or route add-host 172.16.16.105 GW 172.16.16.1

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Route del Delete route

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D:dns configuration file

/etc/resolv.conf DNS File Service nameserver 82.163.143.169

Note: Only primary DNS problems are then used from DNS

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E: Network card configuration file

Two files:

First: Modify/etc/sysconfig/network

Whether to start the network configuration

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Second: each physical NIC corresponding file

/etc/sysconfig/network-scripts/ifcfg-ens33

File with the NIC name behind it

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can be edited manually

Network card restart

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Disable and start the network card with Ifdown ens33 && ifup ens33

F: New Network Command IP

The command consolidates the name of the Ifconfig route, and the IP command runs in the kernel

Run, ifconfig command in the form of a device file

Ip Addr Show

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Port IP addr Show corresponding device

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IP addr Configuration Address IP addr Add 172.16.16.106 dev Ens33

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G: Graphical Network Configuration Tool

1. Running System-config-network-tui on GUI interface (CentOS 6)

Permanently valid after saving

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2. Setup (Centos 7)

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H:netstat Monitoring Network Services

1, Netstat–tnul

T for TCP u stands for UDP n to display L monitor p process in digital

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TCP UDP queue Local address, remote address status process number

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In the monitoring listen the transmission layer is normal, and then ensure the network normal ifconfig

TCP all corresponding link a represents all

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I: Command SS View Network

Deep content from the system-level proc Directory

Netstat is the aggregated information in the statistics proc Directory

SS is the kernel read session table, High efficiency

L monitor e stands for extra m for memory p process N in digital display i print

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Job 1:

1, Nmap sniffer use, need to install through the Yum source

command format usage:nmap [Scan Type (s)] [Options] {target specification}

-V Show-sn for ping scan

For example: Nmap

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2, Tcpdump

3, Wirshark for packet capture analysis

20150908 Linux operation and Maintenance Network Foundation and TCP finite state machine state transition principle, Linux network attribute configuration and network