packet tracer

Dynamic Host Configuration Protocol (DHCP) is a protocol designed by IETF to achieve automatic IP configuration, it can automatically assign IP addresses, subnet masks, default gateways, DNS Server IP addresses, and other TCP/IP parameters to the client. Understanding the DHCP process can help us eliminate problems related to the DHCP service. DHCP is an application based on the UDP layer (that is to say, only UDP packets can be viewed during the Snort detection process). DHCP uses UDP to carry

connection requires a "three-time handshake":First handshake: The client sends a SYN packet (SYN=J) to the server and enters the Syn_send state, waiting for the server to confirm;(That is, make a connection request packet: "I want to send you data, OK?" ”）Second handshake: The server receives the SYN packet, it must confirm the customer's SYN (ACK=J+1), and also

Due to a large number of customers under the core of the room, which unavoidably many large customers, is so-called tall tree catches, the recent computer room some customers are always traffic attacks, the prevention method can only be found specifically attacked IP address, and then in the upper core of the IP configuration of the empty route will attack traffic interception in the backbone layer, so as not to affect the normal use , at present, I have done a mirror port at each core, the upli

http://view.inews.qq.com/a/20161025A0766200QQ in narrowband eraQQ is a narrow band of the most representative of the product, in that network transmission efficiency is lower than the era, we still remember Google's homepage? Why is the simple page of Google so concise?Google was born in 1998, is also in the narrow-band era, you will find its home byte size is less than 1024, why less than 1024 bytes, because the Ethernet MTU (that is, the largest transmission unit) is 1024,google in order to le

) { Console.log ( Req.headers); The request header must include Application/json if (req.headers[' Accept ']! = ' Application/json ') { res.code = ' 4.06 '; return Res.end (); } Res.setoption (' Content-format ', ' Application/json '); Res.end (json.stringify ({ Hello: "World" })); Server.listen (function () { console.log (' server started ');});"Simple description" "1" req.headers[' Accept ']! = ' Application/json ' due to the return of the JSON

First, IntroductionRecently, I've been trying to get a proxy and read the data packets to sniff through traffic. So today I learned how to use Python to grab and unpack the package.Two modules are used firstDpkt (My Side ubuntu16.04 LTS) Python2.7 installed in the defaultPCAP Installation1 Install PypcapThen say, pypcap mainly used to grab packets or sniffer, DPKT used to unpack, I know dpkt is to unpack the transport layer and the transmission layer of the data is quite good, but for the applic

contrast cache No-store, all content does not use the Cache Request packet header and the response packet header have Cache-control Contrast cache mechanism (conditional caching mechanism): Basic principle: 1. Cache hit scenario: The client requests a cache header ID to the cache server, and after the client obtains the identity, it sends a header identification rule to the back-end server, notifying

Packet backpack, a condition evolved from the base backpack. The specific question is this. The specific question is this. A backpack with a capacity of V, and several sets of items, each containing a number of items, which are different, and volume W and value p are different. Objects in the group conflict. The maximum value can be obtained in the case of no more than v. At first glance it seems very difficult to look, in fact, carefully thin

It mainly analyzes the packet format of VLAN. At the same time, the application of vconfig command is explained. pc:10.10.107.168 ap:10.10.107.231 (eth0.100) 1: Add VLAN, use Vconfig. ~# Vconfig BusyBoxv1.10.3 (2012-09-23 02:13:20 CST) multi-call binary Usage:vconfig COMMAND [OPTIONS] ... Create Andremove Virtual Ethernet Devices Options: add [Interface-name] [vlan_id] REM [Vlan-name] Set_flag [Interface-name] [flag-num] [0 | 1] Set_egress_map [Vla

It mainly analyzes the packet format of VLAN. At the same time, the application of vconfig command is explained. pc:10.10.107.168 ap:10.10.107.231 (eth0.100) 1: Add VLAN, use Vconfig. ~# Vconfig BusyBoxv1.10.3 (2012-09-23 02:13:20 CST) multi-call binary Usage:vconfig COMMAND [OPTIONS] ... Create Andremove Virtual Ethernet Devices Options: add [Interface-name] [vlan_id] REM [Vlan-name] Set_flag [Interface-name] [flag-num] [0 | 1] Set_egress_map [Vlan-

The Today's development environment has the following error with the connection datagram, and the error message is as follows: The last packet successfully received from the server is 18,903 milliseconds ago. the last packet sent successful Ly to the server is 18,901 milliseconds ago.; Nested exception is com.mysql.jdbc.exceptions.jdbc4.CommunicationsException:Communications link failure the last Packe

Request Packet Structure: Part One: Request lines (one row in a packet) The request line consists of three parts: the request method (Get/post), the request resource path, the type and version of the Protocol. The second part: The style of the message header (some special meanings of key-value pairs) for some message headers, such as: Content-type=text/html;charset=utf-8. Both server-side and browser-side

Tags: nic option my.cnf Pack uses-name ror add ICAEnvironment: The Ubuntu virtual machine is installed in VirtualBox, the network uses NAT mode, and port forwarding is turned on. There are two problems with accessing MySQL server in a virtual machine from other computers in the LAN: Lost connection to MySQL server at ' reading initial communication packet, System error:0 And Host is not a allowed to connect MySQL 1. Fix lost connection to MySQL serv

Tags: round play learning block div introduction CTI SQL database relative "Error Content": SQL error: Lost connection to MySQL server @ ' Waiting for initial communication packet ', System error:0 "Wrong Generation Passes": appears when linking to MySQL. "Workaround": Open My.ini, Find [mysqld] item, add a sentence after: Skip-name-resolve, save, restart MySQL service can ~The above is to resolve MySQL Error: Lost connection to MySQL server at waitin

LibPcap packet loss problem-Linux Enterprise Application-Linux server application information. The following is a detailed description. Author: Yu Zhu During this time, we checked the high packet loss rate of LibPcap. Many people mentioned this on the internet, but they always suspect that their problems are different from those of others. Environment Description: Snapgear-3.5.0/kernel: linux-2.6.x/uClibc

There are many metrics for describing the performance of a vswitch, such as switching capacity (Gbps), backboard bandwidth (Gbps), throughput, or packet forwarding rate (Mpps. The most important performance indicator of a vswitch is the throughput (Mpps), because it can ultimately reflect the performance indicator of the vswitch application. Users generally go straight to this topic, it depends on the number of packages that the product can forward pe

Cisco held a network lecture entitled "define your router with 256 or fewer bytes". The subject of this lecture is: "the accuracy and performance improvement of network security products forces hackers to successfully launch attacks in the first 256 bytes of the Code, so that they can easily intrude into the network without being noticed ". As a result, Cisco developed a technology named Flexible Packet Management (FPM), which is more widely used than

A heartbeat packet is called a heartbeat packet because it is sent at a fixed time like a heartbeat packet to tell the server that the client is still alive. In fact, this is to maintain a persistent connection. As for the content of this package, there is no special rule, but it is generally a small package, or only contains an empty package of the Baotou. In th

and look for it. I will not explain it. ØADB push c: \ wherever_you_put \ tcpdump/data/local/tcpdump Modify file attributes ADB Shell Su Chmod 6755/data/local/tcpdump Command Line packet capture /Data/local/tcpdump-p-VV-S 0-W/Sdcard/capture. pcap-Which path do you write by the way? (If tcpdump: no suitable device found appears. Make sure that you are using the root permission) ^ C after the packet captur

For a UDP server, if several UDP clients send data to it at the same time, and the UDP server uses a single-thread serial processing method to process received UDP packets, then, when the UPD server has not processed a packet, several other clients send data at the same time, and the data is accumulated together (or overlapped ), as a result, when the UDP server receives data using the recvfrom function next time, the data actually received is a colle