CCNA is the leading IT certification course provided by Cisco for those IT experts working in the networking field. Upon completion of this job, the IT professionals can easily demonstrate to their companies that they understand how to strengthen Cisco ideas into the networking field.
To comprehend the SDN, think about just two technical functions in the IT networking field. One is programming, and the other one is dealing with the entire networking gadgets physically. So the SDN relates to the programming skills, which make it possible for any specific to interact with the Cisco devices. It is helpful to study SDN if any individual is in the networking field, regardless of whether he holds any Cisco certification.
SDN represents Software Defined Network, and besides Cisco, many other suppliers have likewise begun releasing this software-based integration to streamline their production efficiency and communicating with them rapidly. This automation is still in progress, which implies understanding SDN can be a plus for any CCNA. It would always be better to get certified in any higher-level IT certification course provided by Cisco.
They can then use these higher-level Cisco IT certs to get promoted to higher-level ranks and earn more money. In brief, many arguments support both two theories of getting licensed with one additional Cisco technical certification to discover SDN.
The reason behind the SDN popularity increase is also because of some restrictions to traditional networking. Traditional networking utilizes a distributed model where procedures like ARP, EIGRP, STP, and so on can be run independently on every network device, making these networking gadgets independent of interacting without any primary device having control over the whole network. Utilizing an SDN controller, the entire network can be managed and monitored according to the vendor’s requirement.
The SDN and CCNA, when combined with the skills of any IT professional working in the networking field, can be helpful to the individual, so it will be a great concept initially to get CCNA certified — going through the SDN and taking the abilities to the next level by getting other Cisco IT accreditations, which unquestionably requires some real difficult work and preparation and correct planning.
The individuals will need to stick with an excellent plan to plan for their whole career lead through all the Cisco IT accreditation courses. Cisco Exam disposes of can be used as an extra supplement in learning and quickly acquiring the abilities while practicing PASSHOT Cisco practice tests. These tests dispose and practice tests can be readily available all over the web.
The Cisco certified trainers are already preparing the PASSHOT Cisco practice tests, and practicing them guarantees to pass any of the Cisco exams in the first attempt.
Therefore, concluding to the end, it is easy to ascertain that the IT experts can enhance their abilities utilizing IT certification courses, which have now ended up being obligatory for these people to showcase their talent by becoming accredited from worldwide reputed technology giants like Cisco, Google, Amazon, RedHat, and so on. Those who choose to become certified get picked by the employers over their non-IT certified peers.
CCNA certification is considered the most in-demand credential, and it stands among the most popular accreditations offered by Cisco. It would likewise help the candidates get high development in their careers with much better job opportunities and wage increments. CCNA exam would not be that easy for clearing as the preparation needs a lot of hard work and severity. The preparation for this examination ought to likewise be done correctly to clear it in the first attempt.
Let us briefly introduce a few of the suggestions you require to follow for success in the CCNA assessment.
1. Comprehending the Exam
For the prospects, it is extremely vital to have a correct understanding of the sort of difficulty they are going to deal with. This info would be readily available from the Cisco Certification guide, which they could discover on the Cisco site giving all the information about the examination, sort of concerns, designated time, and the passing score.
2. Preparation your Study Schedule
Adequate Study Schedule preparation is highly recommended, without which you may fail to pass the exam. Preparation and arranging the examination well before time and providing yourself an affordable amount of time for preparation is much necessary. This preparation would depend on many other aspects, like the time you could spare for the research study each day, selecting the research study or training approach, and about much you know already.
3. Enroll yourself in a training course
It is highly recommended that registering for an accreditation training course as the examination requires knowledge of lots of topics and subjects and a thorough understanding. The experts or the fitness instructors would have the ability to assist the candidates in understanding the nitty-gritty of a test and enabling them to pass it more quickly. It would be ending up being much comfier to clarify complicated ideas and share issues or experiences with fitness instructors and fellow trainees while preparing for the test. Have a look at the PASSHOT CCNA 200–301 Exam Dumps to gain success in your CCNA Exam.
4. Exam formats
It is considered to be crucial for obtaining an understanding of the test format ahead of time. The test format will convey the number of questions, the type of concerns asked, and weightage for each subject, which is essential to have. A correct understanding of the exam format would help you figure out the time that should be set aside for each case throughout the preparation.
5. Sign up with online forums
Signing up with online neighborhoods and online forums could be beneficial. This would allow you to share experiences and learn the current methods evolved from others’ success or failure stories.
Apart from all this, it would help if you remained calm and composed on the day of your evaluation. Keep your test resources prepared and reach the exam center well on time to prevent any trouble. Understanding the questions completely before responding to and keeping a continuous look is far more necessary during the evaluation.
Follow these research study tips and obtain the PASSHOT CCNA 200–301 Exam Dumps to achieve success in your very first effort.
Today we come to understand the network port mirroring technology.
Port mirroring is to copy the packets of the specified port (source port), VLAN (source VLAN) or CPU (source CPU) to other ports (destination ports). The destination port will be connected to the data monitoring device, and the user will use these data to monitor The device analyzes the packets copied to the destination port for network monitoring and troubleshooting. Without seriously affecting the normal throughput of the source port, the network traffic can be monitored and analyzed through the mirror port.
Source port: It is the monitored port, and the user can monitor and analyze the packets passing through the port.
Source VLAN: It is the VLAN to be monitored. Users can monitor and analyze the packets passing through all ports of this VLAN.
Source CPU: The CPU on the monitored board. The user can monitor and analyze the packets passing through the CPU.
Destination port: It can also be called a monitoring port. This port forwards the received message to the data monitoring device for monitoring and analysis of the message.
Mirror direction:
Incoming direction: Only the packets received from the source port/source VLAN/source CPU are mirrored.
Outgoing direction: Only the packets sent from the source port/source VLAN/source CPU are mirrored.
Bidirectional: Mirror the packets received and sent from the source port/source VLAN/source CPU.
According to the division of mirroring functions, port mirroring is divided into two types:
Flow mirroring: If ACL is configured and enabled on the port, it is considered to be flow mirroring. Flow mirroring only collects data packets filtered by ACL, otherwise it is regarded as pure port mirroring. For ACL traffic collection methods, it is supported to bind standard access lists and extended access lists in the direction of the port (outgoing, incoming, and bidirectional).
Pure port mirroring: mirror the traffic in and out of the port.
According to the scope of mirroring work, port mirroring is divided into two types:
Local mirroring: The source port and destination port are on the same router.
Remote mirroring: The source port and the destination port are distributed on different routers, and the mirrored traffic is encapsulated to achieve cross-router transmission.
The implementation of local port mirroring:
Local port mirroring can mirror all messages (including protocol messages and data messages). It is realized by a local mirroring group, that is, the source port/port in the source VLAN/source CPU and destination port are mirrored locally In the group, the device copies the packets from the source port (or source VLAN) and forwards them to the destination port. The local mirroring group supports cross-board mirroring, that is, the destination port and the source port/port/source CPU in the source VLAN can be on different boards of the same device.
Remote mirroring is divided into cross-layer 2 remote port mirroring and cross-layer 3 remote port mirroring:
Cross-Layer 2 remote port mirroring:
Cross-Layer 2 remote port mirroring can mirror all messages except protocol messages. It is realized by the cooperation of the remote source mirroring group and the remote destination mirroring group.
The user creates a remote source mirroring group on the source device and a remote destination mirroring group on the destination device. The source device copies the source port/source VLAN/source CPU message, broadcasts it in the remote mirroring VLAN through the reflection port, and sends it to the destination device via the intermediate device. After the destination device receives the message, if its VLAN ID is the same as the VLAN ID of the remote mirroring VLAN of the remote destination mirroring group, it forwards it to the destination port.
In this way, the data monitoring device connected to the destination port can monitor and analyze the source port/source VLAN/source CPU packets on the source device. The user needs to ensure the interoperability of the Layer 2 network between the source device and the destination device in the remote mirroring VLAN.
Since the source port/source VLAN/source CPU message will be broadcast in the remote mirroring VLAN of the source device, the local port mirroring function can be realized by adding other ports on the source device to the remote mirroring VLAN.
Mirroring across three layers of remote ports:
Cross-Layer 3 remote port mirroring can mirror all messages except protocol messages. It is realized by the cooperation of remote source mirroring group, remote destination mirroring group and GRE tunnel.
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PSTN (Public Switched Telephone Network) is a switched network used for global voice communications. This network has approximately 800 million users and is the largest telecommunications network in the world today.
In normal life, such as when we use a landline phone to make a call or use a telephone line to dial the Internet at home, we all use this network. One thing that needs to be emphasized here is that the PSTN network existed for the transmission of voice data from the beginning.
PSTN (PublicSwitch Telephone Network) is a telephone network commonly used in our daily lives. As we all know, PSTN is a circuit-switched network based on analog technology. Among many wide area network interconnection technologies, the communication cost required for interconnection through PSTN is the lowest, but its data transmission quality and transmission speed are also the worst, and the PSTN network resource utilization rate is relatively low.
It also refers to POTS. It is a collection of all circuit-switched telephone networks since Alexander Graham Bell invented the telephone. Today, except for the final connection between the user and the local telephone switchboard, the public switched telephone network has been technically fully digitalized.
In relation to the Internet, PSTN provides a considerable part of the long-distance infrastructure of the Internet. In order to use the long-distance infrastructure of the PSTN and share the circuit through information exchange among many users, the ISP needs to pay the equipment owner a fee.
In this way, Internet users only need to pay the Internet service provider. The public switched telephone network is a circuit-switched service based on standard telephone lines, used as a connection method for connecting remote endpoints. Typical applications are the connection between remote endpoints and local LAN and remote users dial-up Internet access.
PSTN can be composed of two parts, one is the switching system; the other is the transmission system, the switching system is composed of telephone switches, and the transmission system is composed of transmission equipment and cables. With the growth of user needs, these two components are constantly developing and improving to meet user needs.
1. The development of the exchange system probably goes through the following stages.
In the era of manual switching, transfers are performed manually. Just like a long time ago, when making a call, an operator will be connected first, and the operator will help you with the transfer.
In the era of automatic switching, step-by-step and crossbar switches were produced.
In the era of semi-electronic switching, electronic technology was introduced into the control part of the switch.
In the era of air division switching, program-controlled switches were created, but analog signals were still transmitted.
In the era of digital switching, with the successful application of PCM pulse code modulation technology, digital program-controlled switches have also been produced, in which digital signals are transmitted.
2. PSTN transmission equipment has evolved from carrier multiplexing equipment to SDH equipment, and cables have also evolved from copper wires to optical fibers.
What PSTN provides is an analog dedicated channel, and the channels are connected via several telephone exchanges. When two hosts or routers need to be connected via PSTN, modems must be used to implement signal analog/digital and digital/analog conversion on the network access side at both ends.
From the perspective of the OSI seven-layer model, PSTN can be seen as a simple extension of the physical layer, and does not provide users with services such as flow control and error control. Moreover, because PSTN is a circuit-switched way, a path is established until it is released, and its full bandwidth can only be used by the devices at both ends of the path, even if there is no data to be transmitted between them. Therefore, this circuit switching method cannot achieve full utilization of network bandwidth.
PSTN access to the network is relatively simple and flexible, usually as follows:
1. Access to the network through ordinary dial-up telephone lines. As long as the modem is connected in parallel on the original telephone lines of the two communication parties, and then the modem is connected to the corresponding Internet equipment. Most Internet devices, such as PCs or routers, are provided with several serial ports, and serial interface specifications such as RS-232 are used between the serial port and the Modem. The cost of this connection method is relatively economical, and the charging price is the same as that of ordinary telephones, which can be applied to occasions where communication is not frequent.
2. Access the network through leased telephone lines. Compared with ordinary dial-up telephone lines, leased telephone lines can provide higher communication speed and data transmission quality, but the corresponding costs are also higher than the previous method. The access mode of the dedicated line is not much different from the access mode of the ordinary dial-up line, but the process of dial-up connection is omitted.
3. The way to connect to the public data exchange network (X.25 or Frame-Relay, etc.) from PSTN via ordinary dial-up or leased dedicated telephone line. It is a better remote way to use this method to realize the connection with remote places, because the public data switching network provides users with reliable connection-oriented virtual circuit services, and its reliability and transmission rate are much stronger than PSTN.
The above is the news sharing from the PASSHOT. I hope it can be inspired you. If you think today’ s content is not too bad, you are welcome to share it with other friends. There are more latest Linux dumps, CCNA 200-301 dumps, CCNP Written dumps and CCIE lab dumps waiting for you.
If you do yoga, meditate, smoke one by one, or eat a lot of refreshing food when you are nervous, please take a break and do so now, because frankly, the content is harder this time!
The voice VLAN function allows the access port to transmit voice data streams from IP phones. When a Cisco IP phone is connected to a switch, it will specify the Layer 3 IP priority and Layer 2 Class of Service (CoS) values in the voice data stream sent; for voice, these two values are both 5, and for For other data streams, the default is 0.
If the data transmission is uneven, the voice quality of the IP phone will be reduced, so the switch supports the quality of service (QoS) based on IEEE 802.1p CoS. 802.1p provides a mechanism to implement QoS at the data link layer. In the 802.1Q relay header, the information of the 802.1p field is included. Looking at the fields in the 802.1Q tag, you will see a field named “Priority”, which contains 802.1p information. QoS uses classification and scheduling to send network traffic from switches in an organized and predictable manner.
The Cisco IP phone is a configurable device that can be configured to include IEEE 802.1p priority in the data stream sent. The switch can also be configured to trust or override the priority assigned by the IP phone-this is exactly what we are going to do. A Cisco IP phone is basically a three-port switch: one is connected to the Cisco switch, one is connected to the PC, and another port is located inside, which is connected to the phone itself.
For the access port connected to the Cisco IP phone, it can be configured to use one VLAN for the voice data flow and another VLAN for the data flow of the device (such as a PC) connected to the phone. The access port of the switch can be configured to send Cisco Discovery Protocol (CDP) packets, and the connected Cisco IP phones can be instructed to send voice data streams to the switch in one of the following ways:
• Send via voice VLAN and add a layer 2 CoS priority value;
• Send via access VLAN and add a layer 2 CoS priority value;
• Send via the access VLAN, but do not add the layer 2 CoS priority value.
The switch can also handle tagged data streams (data streams with the frame type of IEEE 802.1Q or IEEE 802.1p) from devices connected to the access ports of Cisco IP phones. You can configure the layer 2 access port of the switch to send CDP packets and order the Cisco IP phone to set the access port connected to the PC to one of the following modes.
• Trust mode: For the data stream received through the access port connected to the PC, the Cisco IP phone does not make any changes to it, and allows it to pass directly.
• Untrusted mode: For IEEE 802.1Q or IEEE 802.1p frames received through the access port connected to the PC, the IP phone adds the configured Layer 2 CoS value to them (the default is 0). Untrusted mode is the default setting.
Configure voice VLAN
By default, the voice VLAN function is disabled; to enable it, you can use the interface configuration command switchport voice vlan. After the voice VLAN function is enabled, the default CoS priority of the port will be used when sending untagged data streams, and the CoS value of IEEE 802.1Q or IEEE 802.1p data streams is not trusted.
The following is the voice VLAN configuration guide.
• Voice VLAN can only be configured on the access port of the switch; the trunk port does not support voice VLAN, but you can configure it yourself.
• In order for the IP phone to communicate correctly, the voice VLAN must be configured and activated on the switch. To see if there is a voice VLAN, use the privileged EXEC command show v1an-if so, it will be displayed in the output of the command.
• Before enabling voice VLAN, it is recommended to use the global configuration command mls qos to enable QoS on the switch, and use the interface configuration command mls qos trust cos to set the trust status of the port to trust.
• CDP must be enabled on the switch port to which the Cisco IP phone is connected in order to send the configuration. CDP is enabled by default, so unless it is disabled, there will be no problems.
• After voice VLAN is configured, PortFast will be automatically enabled, but after voice VLAN is disabled, PortFast will not be automatically disabled.
• To restore the port to its default settings, use the interface configuration command no switchport voice vlan.
Configure the way the IP phone sends voice data streams
The switch port connected to the Cisco IP phone can be configured to send CDP packets to the IP phone to configure the way the phone sends voice data streams. The phone can send the voice data stream in IEEE 802.1Q frame, and include the layer 2 CoS value; IEEE 802.1p priority tag can be used to give higher priority to the voice, or it can be accessed through the VLAN instead of the native VLAN Transmit all voice. IP phones can also send untagged voice data streams through the access VLAN, or use their own configuration to send voice data streams. In all the above cases, the voice data stream contains a layer 3 IP priority value; for voice, this is usually set to 5.
Now it is time to provide some examples to give you a clear understanding of this. The following example demonstrates how to configure 4 aspects:
(1) How to configure the port connected to the IP phone so that it uses the CoS value to classify the incoming data stream;
(2) How to configure the port to use IEEE 802.1p priority to mark the voice data stream;
(3) How to configure the port to use voice VLAN (10) to transmit all voice data streams;
(4) Finally, how to configure VLAN3 to transmit PC data.
The command mls qos trust cos tells the interface to use the CoS value in the packet to classify the incoming data flow. For untagged packets, the default CoS value of the port is used. But before configuring the trust status of the port, you must use the global configuration command mls qos to enable QoS on the switch.
Note: Until I assigned the same port to two VLANs, I can only do this when one of them is a data VLAN and the other is a voice VLAN.
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SSL is called Secure Sockets Layer. It is a security protocol that guarantees privacy. SSL can prevent the communication between the client and the server from being intercepted and eavesdropped. It can also verify the identities of both parties in the communication and ensure the security of data transmission on the network.
The traditional HTTP protocol does not have a corresponding security mechanism, cannot guarantee the security and privacy of data transmission, cannot verify the identity of the communicating parties, and cannot prevent the transmitted data from being tampered with. Netscape uses data encryption, identity verification and message integrity verification mechanisms to provide security guarantees for network transmission.
The SSL protocol includes several security mechanisms for identity verification, data transmission confidentiality, and message integrity confidentiality.
The authentication mechanism is to use the digital signature method to authenticate the server and the client, and the authentication of the client is optional.
The digital signature can be realized through an asymmetric key algorithm. The data encrypted by the private key can only be decrypted by the corresponding public key. Therefore, the user’s identity can be judged according to whether the decryption is successful. If the decryption result is the same as the fixed message, the authentication is successful. When using digital signatures to verify identity, it is necessary to ensure that the public key of the verifier is authentic, otherwise, illegal users may pretend to be the verifier and communicate with the verifier.
The confidentiality of data transmission is to use a symmetric key algorithm to encrypt the transmitted data. It means that the sender sends the data to the other party before sending the data; after the receiver receives the data, it uses the decryption algorithm and decryption key to obtain the plaintext from the ciphertext. A third party without the decryption key cannot restore the ciphertext to plaintext, thus ensuring the confidentiality of data transmission.
The message verification code is used to verify the integrity of the message during message transmission. The MAC algorithm is an algorithm that converts the key and data of any length into fixed-length data.
1. With the participation of the key, the sender uses the MAC algorithm to calculate the MAC value of the message, and then sends the message to the receiver.
2. The receiving end uses the same key and MAC algorithm to calculate the MAC value of the message, and compare it with the received MAC value
Compare.
If the two are the same, the message has not changed. Otherwise, the message is modified during transmission and the receiving end will discard the
Message.
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AP-Wireless Access Point (WirelessAccessPoint) AP is the HUB in the traditional wired network, and it is also the most commonly used equipment when building a small wireless LAN.
AP is equivalent to a bridge connecting wired and wireless networks. Its main function is to connect various wireless network clients together, and then connect the wireless network to the Ethernet to achieve the purpose of network wireless coverage.
AP is divided into thin and fat?
Thin AP (FITAP):
Also known as wireless bridges, wireless gateways, and so-called “thin” APs.
Popular understanding of thin AP: It cannot be configured by itself, and a dedicated device (wireless controller) is required for centralized control and management configuration.
“Controller + thin AP + router architecture” is generally used for wireless network coverage, because when there are a large number of APs, only the controller is used to manage the configuration, which will simplify a lot of work.
Fat AP (FATAP):
The so-called fat AP in the industry is also called a wireless router. A wireless router is different from a pure AP. In addition to the wireless access function, it generally has two interfaces, WAN and LAN, supports address translation (NAT), and supports DHCP server, DNS and MAC address cloning, as well as VPN access, firewall and other security Features.
What is AC?
The Wireless AccessPoint Controller is a network device used to centrally control the controllable wireless APs in the local area network. It is the core of a wireless network and is responsible for managing all wireless APs in the wireless network. The management of APs includes: Send configuration, modify related configuration parameters, radio frequency intelligent management, access security control, etc. (All ACs and APs currently circulating in the market are from the same manufacturer to manage each other)
What is a POE switch?
POE (PowerOver Ethernet) POE is also known as a local area network-based power supply system (PoL, Powerover LAN) or Active Ethernet (Active Ethernet), sometimes also referred to as Power Over Ethernet, which refers to the existing Ethernet Cat .5 Without any changes to the wiring infrastructure, while transmitting data signals for some IP-based terminals (such as IP telephones, wireless LAN access points, network cameras, etc.), it can also provide DC for such devices Power supply technology.
POE technology can ensure the normal operation of the existing network while ensuring the safety of the existing structured cabling, minimizing costs.
The POE switch can not only provide the transmission function of the ordinary switch, but also provide the power supply function to the other end of the network cable. The integration of power supply + data transmission does not require an additional power supply module or POE power supply module to supply power to the device, and a Cat.5 cable completes all the work.
PoE power supply difference
Standard poe: According to the IEEE802.3af/at specification, it is necessary to first detect the 25K characteristic resistance of the receiving terminal and perform a handshake. Only when the handshake is successful, can the power supply be supplied; otherwise, only data (data) is passed.
Example: Plug the POE power supply into the computer network card, the computer network card will not be burned, only normal Internet access because the data can pass.
Non-standard POE: also called forced supply type, the AC power is supplied as soon as the power is turned on; the receiving terminal is not detected first, and the handshake is not performed, and the power is directly 48V or 54V.
Example: Plug the POE power supply into the computer network card, you can go online normally, but if you don’t negotiate to directly supply 48 or 54V, it may burn the device.
There are roughly 48V, 24V and 12V output voltages (DC) on the market
The software and hardware needed to deploy wireless engineering?
Basic hardware: router POE switch AC controller wireless AP
High-end hardware: firewall router traffic and behavior management bypass main switch floor switch POE switch AC controller wireless AP
Is the greater the power of the AP, the better?
No, the higher the power of the AP, the higher the transmitted signal strength. Literally speaking, it will lead you to a misunderstanding. The stronger the signal, the better, but the stronger the signal is for itself, which is transmitted in the entire wireless network. Signals belong to both parties. Both the transmitter and the receiver will transmit data to each other. If the signal at the transmitter is too strong, it will inevitably affect the return of data from the receiver, which will cause network transmission delays or packet loss.
Popular understanding: In a space, you and another person are talking at the same time, and the other person’s voice is too loud, and your voice is too small, which will cause the other person to not hear what you are saying, thus affecting the quality of the call.
In a large-scale wireless project, what are the key points and the most important points?
Key points of engineering perspective:
design
The actual construction drawing, determining the routing position of the wiring, need to consider such as: concealment, damage to the building (characteristics of the building structure), avoiding power lines and other lines while using the existing space, and pairing cables in the field Necessary and effective protection needs.
The location of the router
The router is generally selected in an underground weak current room (far away from a strong current room to avoid strong electromagnetic interference). Pay attention to ventilation and keep it dry. It is best to have a cabinet and put it together with the core switch.
POE power supply switch location
The location of the POE switch should be selected reasonably, located in the middle of the AP point, to reduce wiring costs and shorten the distance between the switch and the AP.
AP location selection
The point layout of the AP selects the central area of the scene and radiates it toward the periphery. The coverage areas of AP parts should overlap to reduce signal blind areas. The distance between the AP and the POE switch should not exceed 80 meters (a genuine Anpu network cable as an example)
Network cable laying
As the transmission carrier of the network signal, the network cable should be protected during the laying process, and there should be no breaks or dead angles. If necessary, iron pipes should be worn or placed in the roof bridge. Special attention is paid to the principle of high-voltage wires to reduce interference to the signal.
Precautions for practical debugging and post-maintenance:
a. External network and routing: The external network cable is connected in place to ensure the normal Internet access conditions of the line, and the routing is connected to ensure that the routing itself can normally communicate with the Internet. During the construction, the main exchange and the construction floor exchange are connected to ensure the normal communication of the backbone network.
b. Debug walkie-talkie: During the commissioning stage, a set of walkie-talkie equipment needs to be seconded to the mall to facilitate the debugging work.
c. During the construction and debugging stage, sufficient spare parts shall be reserved for AP, switch, network cable, and other construction and debugging hardware.
d. Construction drawings: Before each construction, please ask the constructor to give us two copies of the construction drawings.
Construction network topology: requirements, detailed floor switches, routing information and location, number of APs on each floor, and connection methods.
Construction equipment connection line identification diagram: requirements, routing and switch and AP connection information, corresponding ports, etc., all connection lines are theoretically approximate network cable length (including road-switch-AP).
e. Construction wiring and line marking planning:
Information identification record: AP point Mac information record: when the construction party places the AP location, it is necessary to record the floor number and location number of the AP and the corresponding Mac information (note the corresponding floor plan AP number, for example: 1st floor No. 1 mac information format is 1F- 1: AC:11:22:33:44:AP ). This information is uniformly recorded in the Word document floor shopping mall construction drawing according to the floor distribution or directly manually recorded in the free space on the side of the construction drawing, which is convenient for later maintenance and use.
Wire mark identification record:
(1) The input and output lines of the switch: It is necessary to indicate which floor and location number of the AP connected to the terminal of the identification or serial number, (note the corresponding floor plan AP number, for example: the format of 1st floor 1 is 1F-1), Lines coming in from the external network should also be marked with a cable: “External network access should be marked.”
(2) Interconnection between switches on all floors: The source of the wiring connector with the identification or serial number should be marked at the head of the line interconnection line of the switch. (Pay attention to write the floor and switch label, such as: switch 1 on the first floor, the format is 1F-1 SW)
Check on the spot whether the installed AP is powered on and working normally:
After the construction is completed, the construction personnel shall check all APs on the spot to be energized normally, and the normal state under the power-on condition: the green indicator on the AP is always on. If the routing is in place and running, the software can be used to detect whether the AP normally emits signals and connects to the Internet.
If the above information is completely clear, there is no need for the construction personnel to be on site. If the above information is completely unclear, the construction personnel need to cooperate on site for each commissioning.
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OSPF is a link state routing protocol. It has many advantages such as open standards, rapid convergence, no loops, and easy hierarchical design. The OSPFv2 protocol, which is widely used in IPv4 networks, is too closely related to IPv4 addresses in terms of message content and operating mechanism, which greatly restricts its scalability and adaptability.
Therefore, when we first considered extending OSPF to support IPv6, we realized that this was an opportunity to improve and optimize the OSPF protocol itself. As a result, not only did OSPFv2 be extended for IPv6, but a new and improved version of OSPF was created-OSPF v3.
OSPFv3 is described in detail in RFC2740. The relationship between OSPFv3 and OSPFv2 is very similar to the relationship between RIPng and RIPv2. The most important thing is that OSPFv3 uses the same basic implementation mechanism as OSPFv2-SPF algorithm, flooding, DR election, area, etc. Some constants and variables like timers and metrics are also the same. Another similarity to the relationship between RIPng and RIPv2 is that OSPFv3 is not backward compatible with OSPFv2.
Whether it is OSPFv2 or OSPFv3, the basic operating principles of the OSPF protocol are the same. However, due to the different meanings of the IPv4 and IPv6 protocols and the size of the address space, the differences between them are bound to exist.
Similarities between OSPFv2 and OSPFv3:
1. The router types are the same. Including internal routers, backbone routers, area border routers and autonomous system border routers.
2. The supported area types are the same. Including backbone area, standard area, stub area, NSSA and completely stub area.
3. Both OSPFv2 and OSPFv3 use SPF algorithm.
4. The election process of DR and BDR is the same.
5. The interface types are the same. Including point-to-point links, point-to-multipoint links, BMA links, NBMA links and virtual links.
6. The data packet types are the same, including Hello, DBD, LSR, LSU, and LSA, and the neighbor relationship establishment process is also the same.
7. The calculation method of the metric value has not changed.
The difference between OSPFv2 and OSPFv3:
1. In OSPFv3, the “subnet” concept of OSPFv2 is changed to the “link” concept, and two neighbors on the same link but belonging to different IPv6 subnets are allowed to exchange data packets.
2. The router ID, area ID, and LSA link state ID values are still expressed in 32 bits, so they cannot be expressed in IPv6 addresses.
3. On the link between the broadcast network and the NBMA network, OSPFv2 neighbors are identified by their interface addresses, while neighbors on other types of links are identified by RID. OSPFv3 cancels this inconsistency, and all neighbors on all types of links are identified by RID.
4. OSPFv3 retains the area (or AS) and area (area) flooding range of OSPFv2, but adds a link local flooding range. A new link LSA (Link LSA) is added to carry information that is only associated with neighbors on a single link.
5. The IPv6 protocol uses an authentication extension header, which is a standard authentication process. For this reason, OSPFv3 does not require its own authentication for OSPFv3 packets, it only needs to use IPv6 authentication.
6. Use the link-local address to discover neighbors and complete automatic configuration. IPv6 routers do not forward data packets whose source address is the link address. OSPFv3 believes that each router has assigned its own link address for each physical network segment (physical link) it connects to.
7. In OSPFv2, unknown LSA types are always discarded, while OSPFv3 can treat them as link local flooding range.
8. If an IPv4 address is set on the interface of the router, or a loopback interface is set, OSPFv3 will automatically select the IPv4 address as the router ID, otherwise, you need to set the ID number for the router.
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E-mail is a communication method that provides information exchange by electronic means and is the most used service on the Internet. Through the network’s e-mail system, users can communicate with network users in any corner of the world at a very low price and very fast.
E-mail can be in various forms such as text, image, and sound. At the same time, users can get a lot of free news and special emails, and easily realize easy information search. The existence of e-mail greatly facilitates the communication and exchanges between people and promotes the development of society.
There are many email formats, such as SMTP, POP3, MUA, MTA, etc.
Spam refers to emails sent forcibly without the user’s permission. The emails contain advertisements, viruses, and other content. For users, in addition to affecting normal mail reading, spam may also contain harmful information such as viruses; for service providers, spam can cause mail server congestion, reduce network efficiency, and even become a hacker attacking mail server. tool.
Generally speaking, a dedicated server is used to send spam. Generally speaking, it has the following characteristics:
1. Emails sent without the consent of the user are not relevant to the user.
2. Criminals obtain email addresses through deception.
3. The email contains false advertisements, which will spread a lot of spam.
The anti-spam method is basically divided into technical filtering and non-technical filtering in terms of technology, mainly technical filtering, active filtering, and establishing a filtering mechanism in the process of mail transmission;
Non-technical filtering includes: legal and regulatory documents, unified technical specifications, or social moral advocacy, etc. In the process, mail filtering is divided into server-side filtering and receiving-side filtering. The receiving-side filtering is to check the received mail through the server system program after the mail is sent to the mail server. It is passive filtering, mainly by IP address and keywords. As well as filtering for other obvious characteristics of spam, it is feasible and has a low error rate of normal mail. It is currently one of the main anti-spam methods.
From the beginning of spam, the majority of network providers and Internet companies have begun to make trouble for this. However, it is clear that 30 years of development have not produced effective anti-spam technologies or methods. One of the important reasons is that the situation is huge. The amount of spam and high-complexity filtering technology has not been until recent years, the development of artificial intelligence, machine learning and other disciplines has made progress in anti-spam work.
Common spam filtering methods:
1. Statistical method:
Bayesian algorithm: Based on statistical methods, using the method of marking weights, using known spam and non-spam as samples for content analysis and statistics to calculate the probability that the next email is spam, and generate filtering rules.
Connection/bandwidth statistics: anti-spam is achieved by counting whether the number of attempts to connect to a fixed IP address within a unit time is within a predetermined range, or limiting its effective bandwidth.
Mail quantity limit: Limit the number of mails that a single IP can send in a unit time.
2. List method:
BlackList and WhiteList respectively record the IP addresses or email addresses of known spammers and trusted email senders. This is also one of the more common forms of email filtering. At the beginning of anti-spam activities, this This kind of designated mail filtering is very limited because of the lack of list resources.
3. Source method:
DomainKeys: Use to verify whether the sender of the email is consistent with the claimed domain name and verify the integrity of the email. This technology is a public key + private key signature technology.
SPF (SenderPolicy Framework): The purpose of SPF is to prevent forgery of email addresses. SPF is based on reverse lookup technology to determine whether the specified domain name and IP address of the email correspond exactly.
4. Analysis method:
Content filtering: Filter spam by analyzing the content of emails and then using keyword filtering.
Multiple picture recognition technology: Recognize spam that hides malicious information through pictures.
The sending and receiving of mail generally needs to go through the SMTPServer, and the SMTP server transfers messages through the SMTP (Simple Mail Transfer Protocol) protocol.
The email transmission process mainly includes the following three steps:
① The sender PC sends the mail to the designated SMTPServer.
②The sender SMTP Server encapsulates the mail information in an SMTP message and sends it to the receiver SMTP Server according to the destination address of the mail.
③The recipient receives the mail.
POP3 (Post OfficeProtocol 3) and IMAP (Internet Mail Access Protocol) stipulate how the computer manages and downloads e-mails on the mail server through the client software.
Spam prevention is an IP-based mail filtering technology that prevents the flood of spam by checking the legitimacy of the source IP of the sender’s SMTP Server. The proliferation of spam brings many problems:
① Occupy network bandwidth, cause mail server congestion, and reduce the operating efficiency of the entire network.
②Occupy the recipient’s mailbox space, affecting the reading and viewing of normal mail.
When the firewall is used as a security gateway, all external mails need to be forwarded through the firewall. By checking the IP address of the sender’s SMTP Server, spam can be effectively filtered.
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Today we will learn the detailed explanation of NETCONF protocol.
With the upsurge of SDN over the years, a ten-year-old protocol has once again attracted people’s attention, and it is the NETCONF protocol.
The network configuration protocol NETCONF (Network Configuration Protocol) provides a mechanism for managing network devices. Users can use this mechanism to add, modify, and delete the configuration of network devices, and obtain configuration and status information of network devices.
Through the NETCONF protocol, network devices can provide standardized application programming interface APIs (Application Programming Interface), and applications can directly use these APIs to send and obtain configurations to network devices.
NETCONF (Network Configuration Protocol) is a network configuration and management protocol based on Extensible Markup Language (XML). It uses a simple RPC (Remote Procedure Call)-based mechanism to implement communication between the client and the server. The client can be a script or an application running on the network management system.
The advantages of using the NETCONF protocol are:
1. The NETCONF protocol defines messages in XML format and uses the RPC mechanism to modify configuration information. This can facilitate the management of configuration information and meet the interoperability of equipment from different manufacturers. .
2. It can reduce network failures caused by manual configuration errors.
3. It can improve the efficiency of using the configuration tool to upgrade the system software.
4. Good scalability, devices of different manufacturers can define their own protocol operations to achieve unique management functions.
5. NETCONF provides security mechanisms such as authentication and authentication to ensure the security of message transmission.
The basic network architecture of NETCONF mainly consists of several parts:
1. NETCONFmanager:
NETCONF Manager serves as the Client in the network, which uses the NETCONF protocol for system management of network equipment.
Send a request to the NETCONF Server to query or modify one or more specific parameter values.
Receive alarms and events actively sent by NETCONF Server to learn the current status of the managed device.
2. NETCONFagent:
The NETCONF Agent serves as the server in the network, which is used to maintain the information and data of the managed device and respond to the request of the NETCONF Manager.
The server will analyze the data after receiving the client’s request, and then return a response to the client.
When a device fails or other events, the server uses the Notification mechanism to actively notify the client of the device’s alarms and events, and report the current status change of the device to the client.
3. Configure Datastores:
NETCONF defines the existence of one or more configuration data sets and allows them to be configured. The configuration data set is defined as the complete configuration data set required to make the device enter the desired operating state from its initial default state.
The information that NETCONF Manager obtains from the running NETCONFAgent includes configuration data and status data
NETCONF Manager can modify the configuration data, and by operating the configuration data, make the state of the NETCONF Agent migrate to the state desired by the user.
NETCONF Manager cannot modify the status data. The status data is mainly related to the running status and statistics of the NETCONF Agent.
Like ISO/OSI, the NETCONF protocol also adopts a layered structure. Each layer packages a certain aspect of the protocol and provides related services to the upper layer. The hierarchical structure allows each layer to focus on only one aspect of the protocol, making it easier to implement, and at the same time reasonably decouples the dependencies between each layer, which can minimize the impact of changes in the internal implementation mechanism of each layer on other layers.
The content layer represents a collection of managed objects. The content of the content layer needs to come from the data model, and the original MIB and other data models have defects for configuration management such as not allowing rows to be created and deleted, and the corresponding MIB does not support complex table structures.
The operation layer defines a series of basic primitive operation sets used in RPC. These operations will form the basic capabilities of NETCONF.
The RPC layer provides a simple, protocol-independent mechanism for the encoding of the RPC module. The request and response data of the client and server of the NETCONF protocol are encapsulated by using the <rpc> and <rpc-reply> elements. Normally, the <rpc-reply> element encapsulates the data required by the client or the prompt message of successful configuration , When the client request message has an error or the server-side processing is unsuccessful, the server-side will encapsulate a <rpc-error> element containing detailed error information in the <rpc-reply> element to feed back to the client.
Transport layer: The transport layer provides a communication path for the interaction between NETCONFManager and NETCONF Agent. The NETCONF protocol can be carried by any transport layer protocol that meets the basic requirements.
The basic requirements for the bearer protocol are as follows:
For connection-oriented, a persistent link must be established between NETCONFManager and NETCONF Agent. After the link is established, reliable serialized data transmission services must be provided.
User authentication, data integrity, security encryption, NETCONF protocol user authentication, data integrity, security and confidentiality all rely on the transport layer.
The bearer protocol must provide the NETCONF protocol with a mechanism for distinguishing session types (Client or Server).
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