Networking Essentials (Version 2) – Modules 5 – 8: Network Protocols and Architecture Group Exam

Explanation: The address resolution protocol (ARP) maintains a cache of MAC to IPv4 address mappings on the local computer. If there is no mapping in the cache for a specific IPv4 address, then the ARP process sends an Ethernet broadcast on the local link in an attempt to resolve the destination IPv4 address to a MAC address.

Explanation: The application layer of the TCP/IP model maps to the top three layers of the OSI model, which are the application, presentation, and session layers.

Explanation: A MAC address is composed of 6 bytes. The first 3 bytes are used for vendor identification and the last 3 bytes must be assigned a unique value within the same OUI. MAC addresses are implemented in hardware. A NIC needs a MAC address to communicate over the LAN. The IEEE regulates the MAC addresses.

Explanation: Encapsulation is the process of placing one message format into another message format. An example is how a packet is placed in its entirety into the data field as it is encapsulated into a frame.

Explanation: A communication that has a single source going to a single destination is a unicast. A communication from a single source to a group of destinations is a multicast. A communication from a single source to all destinations on the same local network is a broadcast.

Explanation: The private IP addresses are within these three ranges:
10.0.0.0 – 10.255.255.255
172.16.0.0 – 172.31.255.255
192.168.0.0 – 192.168.255.255

Explanation: The OSI transport layer is functionally equivalent to the TCP/IP transport layer, and the OSI network layer is equivalent to the TCP/IP internet layer. The OSI data link and physical layers together are equivalent to the TCP/IP network access layer. The OSI session layer (with the presentation layer) is included within the TCP/IP application layer.

Explanation: There are two common types of network communication models:
Protocol model – This model closely matches the structure of a particular protocol suite and describes the functions that occur at each layer of protocols within the suite. The TCP/IP model is an example of a protocol model.
Reference model – The primary purpose is to aid in a clearer understanding of the functions and processes necessary for network communications.This type of model does not specify exactly how a function should be accomplished. The OSI model is an example of a reference model.

Explanation: Among the many standards for which the IEEE is responsible, the two major standards are IEEE 802.3 and IEEE 802.11. The IEEE 802.3 standard defines media access control (MAC) for wired Ethernet. The 802.11 standard defines a group of standards for implementing wireless local area networks (WLANs). The other options are standards that are developed and maintained by other standards organizations.

Explanation: 100BASE-T is an Ethernet standard that translates to 100 megabits per second, baseband transmission, and twisted pair cable​.​

Explanation: The IP addresses 201.34.45.0, 192.16.43.67, and 195.124.45.255 are Class C addresses. With the default subnet mask of 255.255.255.0, 192.16.43.67 is a unicast address or host address, 195.124.45.255 is a broadcast address, and 201.34.45.0 is a network address. IP address 226.34.15.78 is a Class D multicast address.

Explanation: Protocols provide rules that define how a message is transmitted across a network. Implementation requirements such as electronic and bandwidth details for data communication are specified by standards. Operating systems are not specified by protocols, but will implement protocols. Protocols determine how and when to send a message but they do not control the contents of a message.

Explanation: A LAN switch populates the MAC address table based on source MAC addresses. When a switch receives an incoming frame with a destination MAC address that is not listed in the MAC address table, the switch forwards the frame out all ports except for the ingress port of the frame. When the destination device responds, the switch adds the source MAC address and the port on which it was received to the MAC address table.

Explanation: The destination IP address is used for end-to-end delivery of data to a remote network. The destination MAC address is used for delivery on a local network. The destination port number identifies the application that should process the data at the destination. Source addresses identify the sender of the data.

Explanation: By dividing the one big network into two smaller network, the network administrator has created two smaller broadcast domains. When a broadcast is sent on the network now, the broadcast will only be sent to the devices on the same Ethernet LAN. The other LAN will not receive the broadcast.

Explanation: A router accepts a packet and accesses its routing table to determine the appropriate exit interface based on the destination address. The router then forwards the packet out of that interface.

Explanation: The default gateway is used to route packets destined for remote networks. The default gateway IP address is the address of the first Layer 3 device (the router interface) that connects to the same network.

Explanation: The default gateway is the address of the device a host uses to access the Internet or another network. If the default gateway is missing or incorrect, that host will not be able to communicate outside the local network. Because the host can access other hosts on the local network, the network cable and the other parts of the IP configuration are working.

Explanation: A router contains a routing table of all locally connected networks and the interfaces that connect to them. The routing tables can also contain the routes that the router uses to reach remote networks. When a router determines that an incoming packet contains the destination host on a remote network, it encapsulates the frame to forward it towards to the next hop router. It uses the MAC address of the interface on the next hop router as the destination MAC address. The MAC address is obtained through ARP.

Explanation: A router contains a routing table of all locally connected networks and the interfaces that connect to them. The routing tables can also contain the routes that the router uses to reach remote networks. Entries can be made to the routing table in two ways. The first is that the router via the use of a routing protocol can be dynamically updated by information received from other routers in the network. The second is that the entries can be manually entered by a network administrator. If the router cannot determine where to forward a packet, it will drop it. Network administrators can configure a default route to keep a packet from being dropped because the path to the destination network is not in the routing table. A default route is the interface through which the router forwards a packet containing an unknown destination IP network address.

Explanation: An IPv4 address is divided into two parts: a network portion – to identify the specific network on which a host resides, and a host portion – to identify specific hosts on a network. A subnet mask is used to identify the length of each portion.

Explanation: When a host sends a packet, it uses the subnet mask to compare the source IPv4 address and the destination IPv4 address. If the network bits match, both the source and destination host are on the same local network. Otherwise, the destination host is on a remote network.

Explanation: In classful IPv4 addressing, a network with the first octet of 198 is a Class C network with the default subnet mask of 255.255.255.0.

Explanation: The Cisco hierarchical network design model divides the network into three distinct layers. The access layer provides connectivity for the users. The distribution layer is used to forward traffic from one local network to another. The core layer represents a high-speed backbone layer between networks. The network layer is part of the OSI model. The Internet layer is part of the TCP/IP model. The application layer is part of both the OSI and TCP/IP models.

Explanation: A switch builds a MAC address table by inspecting incoming Layer 2 frames and recording the source MAC address found in the frame header. The discovered and recorded MAC address is then associated with the port used to receive the frame.