Networking essentials (version 2) - modules 5 - 8: network protocols and architecture group exam

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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

Answers Explanation & Hints:

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.

Answers Explanation & Hints:

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.