ccna 200-301 network simulator ns2 simulator projects

ccna 200-301 network simulator ns2 simulator projects.AD question asks: Why do industrial data communications use a hierarchical OSI reference model (choose 2)? A is correct; B says that the OSI reference model uses the same electronic components from different vendors, saving development and research funds. option C says that the OSI model supports multiple competing standards and therefore provides more business opportunities for device manufacturers, which is incorrect; option D says that the OSI reference model accelerates industry standardization by defining the functions that occur at each layer of the model. Correct; option E says that OSI provides aThe purpose of layering is to make the layers relatively independent of each other, so that changing the functionality of one layer does not affect the other layers.17.Solution.DEF question asks: an inbound access control list is configured on a serial port for the purpose of denying access to ports 21, 23, and 25 to TCP and UDP,What type of packets will be allowed by this ACL? Although this question mentions access control lists, the real test is on your mastery of common protocols. Some common public port numbers to remember are FTP (TCP 20 and 21), Telnet (TCP 23), SMTP-E-mail (TCP 25), DNS (TCP and UDP 53), TFTP (UDP 69), HTTP (TCP 80), POP3 (TCP(of 110). Here, traffic on ports 21, 23, and 25 is filtered, so that means FTP, Telnet, and SMTP traffic is filtered, and the rest is allowed. Therefore, D, E, and F are correct.18. Solution: BThe question asks: What kind of service does DNS provide? DNS provides domain name resolution services, that is, resolving domain names to corresponding IP addresses, such as the domain name of Nanjing University of Technology www.njut.edu.cn IP address 202.119.248.65. So the correct answer is B.Which protocol will be blocked by the access control list?Which protocol will be blocked by the access control list? The ping command uses the echo and echo-replay messages of the ICMP protocol to detect if the link is connected. So if you want to block ping traffic to the network, just filter out the ICMP protocol packets.20. Solution: Question B asks: Hostl wants to ping the router's IP address 192.168.1.254,Based on the ARP table of Hostl shown in the figure, what will Hostl do?