OSI and Network Equip
Which protocol functions at the transport layer of the OSI model?
UDP (User Datagram Protocol) is one of the two main transport-layer protocols. TLS (Transport Layer Security) secures other protocols by adding encryption. IP (Internet Protocol) is the principal protocol used by the network layer. Wi-Fi is a data link layer protocol used by access points for wireless networks.
Which of the following characteristics describes UDP?
UDP (User Datagram Protocol) is useful when a great volume of data must be transferred quickly or in situations where the data changes often and speed is more important than complete data accuracy. In contrast, TCP (Transmission Control Protocol) ensures that a connection or session is established, uses sequencing and checksums, and provides flow control.
Which of the following is an application layer protocol?
Several protocols are used at the application layer, including HTTP (Hypertext Transfer Protocol), SMTP (Simple Mail Transfer Protocol), POP3 (Post Office Protocol, version 3), IMAP4 (Internet Message Access Protocol, version 4), FTP (File Transfer Protocol), Telnet, and RDP (Remote Desktop Protocol). Application layer protocols are used by applications and system utilities. IP (Internet Protocol) is a network layer protocol. TCP (Transmission Control Protocol) is a transport layer protocol. Apache is a web server application.
Which two protocols manage neighbor discovery processes on IPv4 networks?
On IPv4 networks, neighbor discovery is managed by ARP (Address Resolution Protocol) with help from ICMP (Internet Control Message Protocol). IP (Internet Protocol) versions 4 and 6 specify where data should be delivered and enable TCP/IP to internetwork. TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) include a physical address used to find a node on the local network. NDP (Neighbor Discovery Protocol) eliminates the need for ARP and some ICMP functions in IPv6 networks. Ethernet uses physical addresses to find nodes on the local network.
You're getting a duplicate IP address error on your computer and need to figure out what other device on your network is using the IP address 192.168.1.56. What command will show you which MAC address is mapped to that IP address?
The database of IP-to-MAC address mappings is called an ARP table; to view a workstation's ARP table, enter the command arp -a. The command telnet 192.168.1.56 will attempt to connect to a device on the network at the IP address listed. The command tracert 192.168.1.56 will trace a path from the local node to the node at the listed IP address. The netstat -n command lists current connections on the local device, including IP addresses and ports.
A user complains that their computer cannot access email, although the computer can access websites. At which layer of the OSI model should you begin troubleshooting this problem and why?
Because the problem is with some applications (email) and not others (web browser), troubleshooting should begin at the application layer. Email protocols such as SMTP, POP3, and IMAP4 all function at the application layer. Problems at other layers—including the physical, data link, and transport layers—would affect all applications, not just some of them.
You're working on a network performance issue after receiving several trouble tickets from users, and you need to check the configuration of a router in a nearby building. Which utility should you use to access the router securely over the network?
With SSH (Secure Shell), you can securely log on to a device and execute commands on that device, including reading and changing the device's configuration. While Telnet provides similar functionality, it provides little security. SFTP (Secure FTP) is a file-transfer version of SSH and is not designed for interacting with a remote device's configuration. RDP (Remote Desktop Protocol) is a Microsoft proprietary protocol used by Windows Remote Desktop and Remote Assistance client-server utilities to connect to and control a remote Windows computer.
In the event of a fire, a failure policy that ensures all doors remain unlocked is called a __________ policy.
During a fire alert using a fail-open policy, all exit doors stay unlocked so that people can safely leave the building and firefighters can enter the building, even though this might present a security risk for thieves entering the building. A fail-close policy would lock doors in the event power is lost. An emergency power-off switch can quickly shut down a data center's computers, although improper shutdowns are hard on computers and their data
Providing the username for an account on a server provides a potential hacker with sensitive information that could make it easier to hack the server. Server naming conventions might include the server's building location, purpose on the network, or name of the department that runs it or uses it. A web server is typically not considered sensitive enough to require obscuring its building location within a corporate location.
After adding three new servers and a network printer to your network, you're having problems identifying which IP address belongs to each device. You've decided to run an Nmap scan of your network. Which TWO apps could you use to perform this task?
Nmap was originally designed as a command-line utility, which, in Windows, can be run in Command Prompt or PowerShell. It's also available in a GUI form called Zenmap. Nmap does not run in browsers such as Microsoft Edge. You could use a diagramming app such as Microsoft Visio to draw your own representation of your network; however, Visio cannot run Nmap to scan the actual network.
In the client–server model, what is the primary secure protocol used for communication between a browser and web server?
The primary protocol used by web servers and browsers (clients) is HTTP (Hypertext Transfer Protocol). When HTTP is layered on top of an encryption protocol, such as SSL (Secure Sockets Layer) or TLS (Transport Layer Security), the result is HTTPS (HTTP Secure), which secures the transmission.
A network consists of seven computers and a network printer, all connected directly to one switch. Which network topology does this network use?
In a star topology, all devices connect to one central device such as a switch. In a mesh topology, each device connects to multiple other devices. In a hub-and-spoke topology, a central switch connects to multiple peripheral switches that each connect to computers in their areas. A client–server network model is a logical topology, not a physical topology.
Which of the following devices are you likely to find in the MDF? Choose all that apply.
An MDF might contain the demarc (or an extension from the demarc, if the demarc itself is located outside the building), a transceiver that converts the incoming signal from the ISP into Ethernet, other connectivity devices (such as switches and routers), network servers that are accessible by a KVM switch, and transmission media. A network printer should be located in a room where it is easily accessible by network users and not locked away in the MDF.
A computer is unable to access the network. When you check the LED lights near the computer's network port, you discover the lights are not lit. Which layer of the OSI model are you using to troubleshoot this problem?
The lights on the network port blink when bits are crossing the interface. Checking the lights is checking for a successful connection at the physical layer. A successful connection at the network, transport, and application layers must be checked using other tools.
What decimal number corresponds to the binary number 11111111?
The largest possible 8-bit binary number is 11111111, which is equal to 255 in decimal. An IPv4 loopback address can fall anywhere in the range of 127.0.0.1 through 127.255.255.254. When counting 8 bits of zeroes (00000000) as a possibility, there are 256 possible 8-bit values for each octet in an IPv4 address. The decimal number 11,111,111 is equal to 101010011000101011000111 in binary.
You're shopping for a new router, and you've found three models that will meet your needs and your budget. After some recent problems with another router on your network, which of the following metrics do you want to maximize to avoid similar problems with the new router?
MTBF (mean time between failures) is the average amount of time that will pass for devices exactly like this one before the next failure is expected to occur. While any single device might experience a failure much sooner or later, vendors and technicians budget for repairs or replacement of devices based on the advertised MTBF. EOS (end-of-support) is the date when support is withdrawn for older systems. EOL (end-of-life) might refer to the same date as the EOS or might refer to a date before the EOS when the product is no longer being sold or produced. Once a device fails, the average amount of time required to repair the device is called MTTR (mean time to repair)
What type of device does a computer turn to when attempting to connect with a host with a known IP address on another network?
The default gateway is the routing device that nodes on the network turn to for access to the outside world. A DNS (Domain Name Service) server helps to find the IP address when that information is not known. A root server is a type of DNS server. A DHCP (Dynamic Host Configuration Protocol) server manages the dynamic distribution of IP addresses to devices on a network.
As you're working to fix a problem with an application, you make multiple changes at once hoping that something will solve the issues you're having. You end up with more problems than when you started. Which step, if followed correctly, would have prevented this complication?
While identifying the problem, approach each problem individually and solve it before moving on to the next. By the time you reach the steps of testing the theory, establishing a plan of action, and documenting results, solving multiple problems at once is likely already causing more problems.
When running a scan on your computer, you find that a session has been established with a host at the address 208.85.40.44:443. Which application layer protocol is in use for this session? What command-line utility might you use to determine the domain name of the other computer?
Port 443 indicates this is an HTTPS session; nslookup can identify the domain name of the host at that IP address. Telnet uses port 23. IMAP4 uses port 143. RDP uses port 3389. The hostname utility can provide the FQDN for the local device, but not for the remote device.
If you are connected to a network that uses DHCP and you need to terminate your Windows workstation's DHCP lease, which command would you use?
The command ipconfig /release releases the IP address when dynamic IP addressing is being used. The command ipconfig /renew leases a new IP address from a DHCP server. The ifconfig command is a Linux command. While you can use ifconfig to release an IP address, you don't accomplish this with the /release parameter.