1.
Which of the following best describes the main function of OSI Layer 1 protocols?
Correct Answer
B. Delivery of bits from one device to another
Explanation
The main function of OSI Layer 1 protocols is to deliver bits from one device to another. This layer is responsible for the physical transmission of data over the network, including the electrical, mechanical, and procedural aspects of the communication. It ensures that the bits are properly encoded, transmitted, and received between devices.
2.
Which of the following typically connects to a four-wire line provided by a telco?
Correct Answer
B. CSU/DSU
Explanation
CSU/DSU, which stands for Channel Service Unit/Data Service Unit, typically connects to a four-wire line provided by a telco. CSU/DSU is a device used in telecommunications to convert digital data from a router into a format that can be transmitted over a telecommunications line, and vice versa. It provides the interface between the router and the telco's line, allowing for the transmission of data over the network. Therefore, CSU/DSU is the correct answer for this question.
3.
Which of the following typically connects to a V.35 or RS-232 end of a cable when cabling a leased line?
Correct Answer
B. CSU/DSU
Explanation
When cabling a leased line, the CSU/DSU (Channel Service Unit/Data Service Unit) typically connects to a V.35 or RS-232 end of a cable. The CSU/DSU is a device used to connect a customer's equipment to a digital line provided by a telecommunications carrier. It provides signal conversion, line conditioning, and error detection functions. The CSU/DSU is responsible for converting the data from the customer's equipment into a format that can be transmitted over the leased line and vice versa.
4.
On a point-to-point WAN link using a leased line between two routers located hundreds of miles apart, what devices are considered to be the DTE devices?
Correct Answer
A. Routers
Explanation
In a point-to-point WAN link using a leased line, routers are considered to be the DTE (Data Terminal Equipment) devices. DTE devices are the end devices that originate and terminate the data transmission. In this scenario, the routers located at each end of the link serve as the DTE devices as they receive and send data across the leased line. The other options listed, such as CSU/DSU (Channel Service Unit/Data Service Unit) and central office equipment, are not DTE devices but rather components that facilitate the connection and transmission of data between the DTE devices.
5.
Which of the following functions of OSI Layer 2 is specified by the protocol standard for PPP, but is implemented with a Cisco proprietary header field for HDLC?
Correct Answer
E. Identifying the type of protocol that is inside the frame
Explanation
The function of identifying the type of protocol that is inside the frame is specified by the protocol standard for PPP, but Cisco uses a proprietary header field for HDLC to implement this function. This means that while PPP follows the standard protocol for identifying the protocol type, Cisco's HDLC uses its own header field for the same purpose.
6.
Imagine that Router1 has three point-to-point serial links, one link each to three remote routers. Which of the following is true about the required HDLC addressing at Router1?
Correct Answer
E. None of these answers are correct.
Explanation
The correct answer is None of these answers are correct because HDLC addressing does not use specific addresses like 1, 2, and 3, or any specific range between 1 and 1023, or between 16 and 1000. HDLC addressing uses the HDLC address field to identify the specific destination router, but there is no requirement for the addresses to be sequential or within a specific range. Therefore, none of the given options are correct.
7.
What is the name of the Frame Relay field used to identify Frame Relay virtual circuits?
Correct Answer
A. Data-link connection identifier
Explanation
The correct answer is Data-link connection identifier. In Frame Relay, the Data-link connection identifier (DLCI) is used to identify the virtual circuits. The DLCI is a unique identifier assigned to each virtual circuit and is used by the Frame Relay devices to determine the destination of the incoming frames.
8.
Which of the following is true about Frame Relay virtual circuits (VCs)?
Correct Answer
B. Multiple VCs can share the same access link.
Explanation
Multiple VCs can share the same access link in Frame Relay. This means that multiple virtual circuits can be established and operate over a single physical connection. This allows for more efficient use of network resources and reduces the need for separate physical links for each VC. Each VC is identified by a unique Data Link Connection Identifier (DLCI), but they can all be transmitted over the same access link.
9.
Which of the following are functions of OSI Layer 3 protocols?
Correct Answer(s)
A. Logical addressing
C. Path selection
Explanation
OSI Layer 3 protocols are responsible for logical addressing and path selection. Logical addressing involves assigning unique addresses to devices on a network, allowing them to communicate with each other. Path selection refers to the process of determining the best route for data packets to travel from the source to the destination. These functions are essential for efficient and reliable communication within a network. Physical addressing, arbitration, and error recovery are not specific functions of Layer 3 protocols, making them incorrect choices.
10.
Imagine that PC1 needs to send some data to PC2, and PC1 and PC2 are separated by several routers. What are the largest entities that make it from PC1 to PC2?
Correct Answer(s)
C. Packet
E. L3 PDU
Explanation
When PC1 needs to send data to PC2, the data is divided into smaller units called packets. These packets are then sent over the network and are responsible for carrying the actual data from PC1 to PC2. Therefore, the largest entities that make it from PC1 to PC2 are the packets. Additionally, the L3 PDU (Protocol Data Unit) also plays a role in this process as it encapsulates the packets and adds necessary routing information.
11.
Imagine a network with two routers that are connected with a point-to-point HDLC serial link. Each router has an Ethernet, with PC1 sharing the Ethernet with Router1, and PC2 sharing the Ethernet with Router2. When PC1 sends data to PC2, which of the following is true?
Correct Answer
A. Router1 strips the Ethernet header and trailer off the frame received from PC1, never to be used again.
Explanation
In this scenario, Router1 acts as a bridge between the Ethernet network and the HDLC serial link. When PC1 sends data to PC2, Router1 receives the frame from PC1 and removes the Ethernet header and trailer. Since the frame is being sent over the HDLC serial link, the Ethernet header and trailer are not needed and are discarded by Router1. Router1 then encapsulates the remaining data (payload) in an HDLC header and sends it to Router2. Router2 will then extract the Ethernet frame from the HDLC header and forward it to PC2. Therefore, the statement "Router1 strips the Ethernet header and trailer off the frame received from PC1, never to be used again" is correct.
12.
Which of the following are valid Class C IP addresses that can be assigned to hosts?
Correct Answer
B. 200.1.1.1
Explanation
The given IP address, 200.1.1.1, falls within the range of Class C IP addresses. In Class C, the first octet ranges from 192 to 223, indicating that this IP address is valid for assignment to hosts.
13.
What is the range of values for the first octet for Class A IP networks?
Correct Answer
D. 1 to 126
Explanation
Class A IP networks have a first octet range of 1 to 126. This range allows for a total of 126 possible values for the first octet, with the value 0 reserved as a default network address and 127 reserved for loopback testing. The range of 1 to 126 is used to designate the network address, while the remaining three octets are used to identify specific hosts within the network.
14.
PC1 and PC2 are on two different Ethernets that are separated by an IP router. PC1's IP address is 10.1.1.1, and no subnetting is used. Which of the following addresses could be used for PC2?
Correct Answer(s)
D. 9.1.1.1
E. 1.1.1.1
Explanation
PC1's IP address is 10.1.1.1, which means it is on a network with a subnet mask of 255.0.0.0. This means that any IP address that starts with 10.x.x.x can be on the same network as PC1. Therefore, 10.1.1.2 is a valid address for PC2. However, 10.2.2.2 and 10.200.200.1 are on different networks and cannot be used for PC2. Similarly, 9.1.1.1 and 1.1.1.1 are on different networks and cannot be used for PC2.
15.
Each Class B network contains how many IP addresses that can be assigned to hosts?
Correct Answer
D. 65,534
Explanation
Each Class B network has a total of 65,534 IP addresses that can be assigned to hosts. This is because Class B networks have a subnet mask of 16 bits, which allows for 2^16 (65,536) possible IP addresses. However, the first and last IP addresses in each network are reserved for network identification and broadcast respectively, leaving 65,534 addresses available for hosts.
16.
Each Class C network contains how many IP addresses that can be assigned to hosts?
Correct Answer
D. 254
Explanation
Each Class C network has a total of 256 IP addresses. However, out of these 256 addresses, one address is reserved for network identification and another address is reserved for broadcast, leaving 254 addresses that can be assigned to hosts. Therefore, the correct answer is 254.
17.
Which of the following does a router normally use when making a decision about routing TCP/IP packets?
Correct Answer
C. Destination IP address
Explanation
A router normally uses the destination IP address when making a decision about routing TCP/IP packets. The destination IP address identifies the intended recipient of the packet, allowing the router to determine the appropriate next hop or outgoing interface for forwarding the packet towards its destination. The source MAC address and source IP address are used for addressing and identification purposes, but they are not typically used by the router to make routing decisions. The destination MAC address is used at the data link layer for local network communication, but it is not relevant for routing packets between different networks.
18.
Which of the following are true about a LAN-connected TCP/IP host and its IP routing (forwarding) choices?
Correct Answer(s)
B. The host sends packets to its default gateway if the destination IP address is in a different class of IP network than the host.
C. The host sends packets to its default gateway if the destination IP address is in a different subnet than the host.
Explanation
A LAN-connected TCP/IP host will send packets to its default gateway if the destination IP address is in a different class of IP network than the host. This is because different classes of IP networks have different network addresses, and the default gateway is responsible for routing packets between different networks. Additionally, the host will also send packets to its default gateway if the destination IP address is in a different subnet than the host. Subnets are smaller divisions of a network, and the default gateway is needed to route packets between different subnets within the same network.
19.
Which of the following are functions of a routing protocol?
Correct Answer(s)
A. Advertising known routes to neighboring routers.
C. Learning routes, and putting those routes into the routing table, for routes advertised to the router by its neighboring routers.
Explanation
A routing protocol is responsible for advertising known routes to neighboring routers, allowing them to learn about the available network paths. It also learns routes for subnets directly connected to the router and adds those routes to the routing table. Additionally, it learns routes from neighboring routers and adds them to the routing table, enabling the router to forward IP packets based on their destination IP addresses.
20.
Which of the following protocols allows a client PC to discover the IP address of another computer based on that other computer's name?
Correct Answer
C. DNS
Explanation
DNS (Domain Name System) is the correct answer because it is the protocol that allows a client PC to discover the IP address of another computer based on that other computer's name. DNS works by translating domain names (e.g., www.example.com) into IP addresses (e.g., 192.168.1.1) that can be understood by computers. This translation process is essential for establishing connections and communication between devices on a network. ARP (Address Resolution Protocol) and RARP (Reverse Address Resolution Protocol) are used for mapping IP addresses to MAC addresses, while DHCP (Dynamic Host Configuration Protocol) is used for automatically assigning IP addresses to devices on a network.
21.
Which of the following protocols allows a client PC to request assignment of an IP address as well as learn its default gateway?
Correct Answer
D. DHCP
Explanation
DHCP (Dynamic Host Configuration Protocol) allows a client PC to request assignment of an IP address as well as learn its default gateway. DHCP is a network protocol that enables a server to automatically assign IP addresses and other network configuration parameters to devices on a network. When a client PC connects to a network, it can send a DHCP request to the DHCP server, which will then assign it an IP address and provide information about the default gateway, DNS servers, and other network settings.