Where does routing occur within the DoD TCP/IP reference model?
Answer : B
Explanation: The picture below shows the comparison between TCP/IP model & OSI model. Notice that the Internet Layer of TCP/IP is equivalent to the Network Layer which is responsible for routing decision.
Which of the following statements describe the network shown in the graphic? (Choose
Answer : A,F
Explanation: Only router can break up broadcast domains so in the exhibit there are 2 broadcast domains: from e0 interface to the left is a broadcast domain and from e1 interface to the right is another broadcast domain ->. Both router and switch can break up collision domains so there is only 1 collision domain on the left of the router (because hub doesnt break up collision domain) and there are 6 collision domains on the right of the router (1 collision domain from e1 interface to the switch + 5 collision domains for 5 PCs in Production) ->.
A network interface port has collision detection and carrier sensing enabled on a shared
twisted pair network. From this statement, what is known about the network interface port?
Answer : C
Explanation: Modern Ethernet networks built with switches and full-duplex connections no longer utilize CSMA/CD. CSMA/CD is only used in obsolete shared media Ethernet (which uses repeater or hub).
Host 1 is trying to communicate with Host 2. The e0 interface on Router C is down.
Answer : A,D
Explanation: Host 1 is trying to communicate with Host 2. The e0 interface on Router C is down. Router C will send ICMP packets to inform Host 1 that Host 2 cannot be reached.
Refer to the exhibit.
Answer : E
Explanation: To elect the root bridge in the LAN, first check the priority value. The switch having the lowest priority will win the election process. If Priority Value is the same then it checks the MAC Address; the switch having the lowest MAC Address will become the root bridge. In this case, switch C has the lowest MAC Address so it becomes the root bridge.
Which layer in the OSI reference model is responsible for determining the availability of the
receiving program and checking to see if enough resources exist for that communication?
Answer : E
Explanation: This question is to examine the OSI reference model. The Application layer is responsible for identifying and establishing the availability of the intended communication partner and determining whether sufficient resources for the intended communication exist.
Refer to the graphic.
Answer : A
Explanation: Whereas switches can only examine and forward packets based on the contents of the MAC header, routers can look further into the packet to discover the network for which a packet is destined. Routers make forwarding decisions based on the packet's network- layer header (such as an IPX header or IP header). These network-layer headers contain source and destination network addresses. Local devices address packets to the router's MAC address in the MAC header. After receiving the packets, the router must perform the following steps: 1. Check the incoming packet for corruption, and remove the MAC header. The router checks the packet for MAC-layer errors. The router then strips off the MAC header and examines the network-layer header to determine what to do with the packet. 2. Examine the age of the packet. The router must ensure that the packet has not come too far to be forwarded. For example, IPX headers contain a hop count. By default, 15 hops is the maximum number of hops (or routers) that a packet can cross. If a packet has a hop count of 15, the router discards the packet. IP headers contain a Time to Live (TTL) value. Unlike the IPX hop count, which increments as the packet is forwarded through each router, the IP TTL value decrements as the IP packet is forwarded through each router. If an IP packet has a TTL value of 1, the router discards the packet. A router cannot decrement the TTL value to 1 and then forward the packet. 3. Determine the route to the destination. Routers maintain a routing table that lists available networks, the direction to the desired network (the outgoing interface number), and the distance to those networks. After determining which direction to forward the packet, the router must build a new header. (If you want to read the IP routing tables on a Windows 95/98 workstation, type ROUTE PRINT in the DOS box.) 4. Build the new MAC header and forward the packet. Finally, the router builds a new MAC header for the packet. The MA
A router has two Fast Ethernet interfaces and needs to connect to four VLANs in the local
network. How can you accomplish this task, using the fewest physical interfaces and
without decreasing network performance?
Answer : D
Explanation: A router on a stick allows you to use sub-interfaces to create multiple logical networks on a single physical interface.
Match the terms on the left with the appropriate OSI layer on the right. (Not all options are
A network administrator is verifying the configuration of a newly installed host by
establishing an FTP connection to a remote server. What is the highest layer of the
protocol stack that the network administrator is using for this operation?
Answer : A
Explanation: FTP belongs to Application layer and it is also the highest layer of the OSI model.
Refer to the exhibit. Complete this network diagram by dragging the correct device name or
description to the correct location. Not all the names or descriptions will be used.
A receiving host computes the checksum on a frame and determines that the frame is
damaged. The frame is then discarded. At which OSI layer did this happen?
Answer : D
Explanation: The Data Link layer provides the physical transmission of the data and handles error notification, network topology, and flow control. The Data Link layer formats the message into pieces, each called a data frame, and adds a customized header containing the hardware destination and source address. Protocols Data Unit (PDU) on Datalink layer is called frame. According to this question the frame is damaged and discarded which will happen at the Data Link layer.
Which of the following correctly describe steps in the OSI data encapsulation process?
Answer : A,D
Explanation: The transport layer segments data into smaller pieces for transport. Each segment is assigned a sequence number, so that the receiving device can reassemble the data on arrival. The transport layer also use flow control to maximize the transfer rate while minimizing the requirements to retransmit. For example, in TCP, basic flow control is implemented by acknowledgment by the receiver of the receipt of data; the sender waits for this acknowledgment before sending the next part. The Network layer (Layer 3) has two key responsibilities. First, this layer controls the logical addressing of devices. Second, the network layer determines the best path to a particular destination network, and routes the data appropriately.
Refer to exhibit:
Answer : C,F
Explanation: While transferring data through many different networks, the source and destination IP addresses are not changed. Only the source and destination MAC addresses are changed. So in this case Host A will use the IP address of Host C and the MAC address of E0 interface to send data. When the router receives this data, it replaces the source MAC address with its own E1 interfaces MAC address and replaces the destination MAC address with Host Cs MAC address before sending to Host C.
What is the difference between a CSU/DSU and a modem?
Answer : D
Explanation: CSU/DSU is used to convert digital signals from a router to a network circuit such as a T1, while a modem is used to convert digital signals over a regular POTS line.