Online interview short answer

What is TRUNK? A: There are two links in the exchange environment. One is the access link and the other is the TRUNK (relay) link. The access link only belongs to one VLAN, while the TRUNK can carry multiple VLANs, the TRUNK uses VLAN identifiers in two encapsulation modes: 802.1Q and ISL. 2. What is the application of the PPP protocol? PPP is currently one of the most widely used protocols on the Wide Area Network. It has the advantages of simplicity, user verification capability, and IP Address allocation. Domestic dial-up Internet access establishes a communication link between the client and the access server of the carrier through PPP. At present, broadband access is becoming a trend to replace dial-up Internet access. In the ever-changing days of broadband access technology, PPP is also a new application. A typical application is that in the ADSL (asymmetric data user Loop, asyuncrical Digital Subscriber Loop) access mode, PPP and other protocols jointly derive a new protocol that meets the broadband access requirements, for example, PPPoE (PPP over Ethernet) and PPPoA (PPP over ATM ). Using Ethernet resources to run PPP over Ethernet for user authentication and access is called PPPoE. PPPoE protects users' Ethernet resources and meets ADSL access requirements. It is currently the most widely used technical standard in ADSL access methods. Similarly, PPPoA is used to manage user authentication by running the PPP protocol on an ATM (Asynchronous Transfer Mode) network. It works in the same way as PPPoE. The difference is that it runs on an ATM network, while PPPoE runs on an Ethernet network, so it must adapt to the ATM and Ethernet standards respectively. 3. Briefly describe the OSPF operation process ① the router sends the HELLO message; ② establishes the adjacent relationship; ③ forms the link state ④ SPF algorithm calculates the Optimal Path ⑤ forms the route table 4, what is the difference between a vswitch and a vro? A: Yes. ① The operation is at a different OSI level. The switch works at the Layer 2 data link layer of OSI, And the router works at the Layer 3 network layer of OSI. ② different addressing modes: The switch is addressable Based on the MAC address, vro Based on IP address addressing ③ different forwarding speeds: vswitch forwarding speed is fast and vro forwarding speed is relatively slow. 5. What is network maintenance? 1. Network Infrastructure: physical security, such as data centers, servers, route exchange devices, and users' PCs; 2. network operating systems: leakage Prevention, Intrusion Prevention, permissions, users, and key management; 3. network applications: users, permissions, and installation control; 4. Basic Security Operation Training for users (users; 5. Develop a complete network operation and maintenance document and log management; 6. system and data disaster recovery mechanisms. 6. What layer does the TCP/IP reference model have? Answer: application layer, transmission layer, Internet connection layer, and network interface layer. 7. What is the difference between Static Routing and dynamic routing. Static Routing is manually configured by the Administrator. It is suitable for simple networks or special routing control. Dynamic Routing is automatically maintained by the dynamic routing protocol without manual intervention. It is suitable for complex and large-scale networks. 8. Do you know the Management Distance of OSPF, RIP, and static routes? They are: 110, 120, and 19. There is a machine in the company that cannot access the Internet, while other computers can access the Internet. The conditions are as follows: The computer is a Windows XP system. The computer can access the company's internal computer, but cannot access the Internet. Analyze the causes. 1. Run the command ipconfig/all to view network configurations, such as IP addresses, gateways, and DNS. 2. Run the command ping to check the connectivity between the gateway and DNS. 3. Use a proxy to access the Internet, check whether the browser connection settings are correct. 4. Check whether the local firewall and anti-virus software prevent access to internet5. Check other browser settings. 6. Check whether the gateway or proxy blocks ip address or mac address 10 and ARP of the machine? ARP is used to convert the IP address connected to the same online computer to the physical address 11 of the machine. What protocol is used for PING? Differences between ICMP12, cisco, and Huawei Common commands. cisco Huawei show displayno shutdown undo shutdownconfigure terminal system-viewshow run display current-configurationend returnhostname sysnameaccess-list aclwrite saveerase deleteencapsulation link-protocol13, commonly used protocol port number. 21/tcp FTP File Transfer Protocol 22/tcp SSH Secure Login, file transfer (SCP) and port redirection 23/tcp Telnet insecure text Transfer 25/tcp SMTP Simple Mail Transfer Protocol (E-mail) 69/udp TFTP Trivial File Transfer Protoc Ol (micro File Transfer Protocol) 80/tcp HTTP Hypertext Transfer Protocol (WWW) 110/tcp POP3 Post Office Protocol (E-mail) 443/tcp HTTPS used for securely transferring web pages 3389/tcp Remote Access 5631/tcp 5632/udp pcanywhere port number 14, commonly used network commands, and instructions for use. ARP-a: view the local ARP table Netstat-a: Display All active TCP connections of the Local Machine and TCP and UDP ports that the computer listens on Netstat-n. display the Tracert packet tracing of active TCP/IP connections. diagnosis (route tracking) 15. For the batch processing below, please explain the role of each line of commands. @ echo offcd/D: \ test \ DB net stop mssqlserver \ pause MSSQL Server set Today = % date :~ 0, 4% % date :~ 5, 2% % date :~ 8, 2% \ set the time "C: \ Program Files \ WinRAR \ RAR.exe" A-S too today).rar test. MDF test. LDF \ use WINRAR to compress the library file. net start mssqlserver \ start MSSQL Server. net use \ IP address \ d $ \ backup "123456"/user: "administrator" \ connect to the remote server copy D: \ test \ DB \ %today).rar \ IP address \ d $ \ backup \ REMOTE backup WinRAR database file @ echo transfer completed \ Print text "transfer completed" 16, what types of disk RAID are commonly used? Write down their rough descriptions and differences. Currently, RAID 0, RAID 1, RAID 5, and RAID (0 + 1) are commonly used ). RAID 0 has the fastest access speed but is not fault-tolerant. RAID 1 is completely fault-tolerant, but the cost is relatively high, the disk usage is 50% RAID 5 with multi-task and fault-tolerant features when writing overhead RAID 0 + 1 fast, completely fault-tolerant, but high cost 17, Class a ip address, Class B IP address, what are the numerical ranges of class c ip addresses? What does 10.201.40.0/23 represent? Class a ip Address: The number range of the first segment is 1 ~ Category B IP Address: The number range of the first segment is 128 ~ 191C type IP Address: The number range of the first segment is 192 ~ 22310.201.40.0/23 indicates A Class a ip address. Its subnet mask is 1 at the first 23 locations, that is, 11111111 11111111 11111110 00000000, expressed in decimal format as 255.255.254.018. In the firewall, which of the following methods can be used to set the port, target address, source address, and Protocol character. 19. What are the most basic concepts of DDoS attacks? Concept: the most basic DoS attack is to use reasonable service requests to occupy too many service resources, so that the server cannot process valid user commands. A large number of waiting TCP connection networks on the attacked host are filled with a large number of useless data packets. The source address is fake to create high-traffic useless data, resulting in network congestion, make the affected host unable to communicate with the outside world and use the service provided by the affected host or the defects in the transmission protocol to repeatedly send specific service requests at high speed, if the affected host fails to process all normal requests in a timely manner, the system will crash. 20. What is IP spoof? IP spoof is IP spoofing. We can say that a host device impersonates the IP address of another host and communicates with other devices to achieve a certain purpose. 21. Mainstream firewall manufacturers and product brands (two in China and two in other countries): tianrongxin firewall. main products network Guard firewall NGFW4000-UF and NGFW4000 series. lenovo network royal Power V product series Huawei Eudemon firewall (Eudemon 100E/200/200 S) Foreign: cisco pix (now changed to ASA) Juniper netscreen Series