Understanding Network Fundamentals: A CCNA Exploration of OSI Layers, Routing, and Subnetting
CCNA 1: Network Fundamentals
Chapter 5: Routing and Switching Essentials
Encapsulation at OSI Layer 3
Q: What information is added during encapsulation at OSI Layer 3?
A: IP source address and destination address
System Offline Behavior
Q: Which of the following is correct for a system offline?
A: No contacts the destination before sending a package.
Preventing Endless Loops in IP Packets
Q: Which IP packet field will prevent endless loops?
A: Time to Live (TTL)
Router Packet Forwarding
Q: What portion of the address of the network layer using a router to forward packets?
A: Network portion
Default Gateway Identification
Q: Refer to the exhibit (not provided). With the network of the presentation, what would be the default gateway address for host A in the 192.133.219.0 network?
A: 192.133.219.1
Impact of Incorrect Default Gateway Configuration
Q: If the default gateway is configured incorrectly on the host, what is the impact on communications?
A: The host can communicate with other hosts on the local network but cannot communicate with hosts on remote networks.
Purpose of a Default Gateway
Q: What is the purpose of a default gateway?
A: It identifies the device that allows computers on the local network to communicate with other network devices.
Types of Routing
Q: What kind of routing uses information that is introduced to the routing table manually?
A: Static routing
Router Actions for Unknown Destination Networks
Q: When the destination network is not in the list of the routing table of a Cisco router, what are the two possible actions that the router could do? (Choose two.)
- The router discards the packet.
- The router forwards the packet to the interface specified by the default route entry.
Factors for Grouping Hosts into a Network
Q: What are the key factors that must be taken into account when grouping hosts into a common network? (Choose three.)
- Purpose
- Location
- Property
Routing Table Entry Component
Q: What is a component of an entry in the routing table?
A: Next-hop address
Intermediary Devices for Network Security
Q: What intermediary devices can be used to implement security between networks? (Choose two.)
- Router
- Firewall
Common Problems in Large Networks
Q: What are the three common problems that presents a large network? (Choose three.)
- Performance degradation
- Security issues
- Host ID conflicts (this option seems out of place, consider replacing it with a more relevant issue)
Determining Broadcast Domains
Q: Refer to the exhibit (not provided). All devices shown in the presentation have factory default settings. How many broadcast domains are represented in the topology shown?
A: 4
Statements about Routes and Their Use
Q: What are the three true statements about the routes and their use? (Choose three.)
- If the destination network connects directly, the router forwards the packet to the destination host.
- If there is no route to the destination network and a default route is present, the router forwards the packet to the next-hop router.
- If the source host has a configured default gateway, it can forward the packet to a remote network via that route.
Identifying Packet Forwarding Address
Q: Refer to the exhibit (not provided). A network administrator attempts to resolve a connectivity problem and must determine the address used to forward network packets out of the network. If using the command netstat -r, how can the administrator identify the address to which all hosts send packets with a destination outside the network?
A: Look for the default gateway address (usually denoted by a destination of 0.0.0.0) in the routing table output.
Resolving Excessive Broadcasts
Q: Refer to the exhibit (not provided). A network administrator warns that too many broadcasts are on the network. What are the two steps for the network administrator to resolve this problem? (Choose two.)
- Replace hubs (if any) with switches to segment the network.
- Divide the network into subnets using a subnet mask like 255.255.255.192 (or /26).
Describing Routing in a Topology
Q: Refer to the exhibit (not provided). The presentation network is fully functioning. What two statements correctly describe the routing for the topology shown? (Choose two.)
A: Provide the specific statements based on the exhibit, focusing on next-hop addresses used by specific routers to reach other networks.
Characteristics of Dynamic Routing Protocols
Q: What are the two characteristics commonly associated with dynamic routing protocols? (Choose two.)
- Provide routers with updated routing tables.
- Consume bandwidth to exchange route information.
Purpose of a Default Route
Q: Which statement describes the purpose of a default route?
A: A host uses a default route to transfer data to a host outside the local network when no other route to the destination exists.
Chapter 6: Subnetting Basics
Network Prefix for an IP Addressing Scheme
Q: Refer to the exhibit (not provided). Which network prefix will work with the IP addressing scheme shown in the graph?
A: /27
Valid Host Addresses
Q: Which IPv4 subnetted addresses represent valid host addresses? (Choose three.)
- 172.16.4.155 /26
- 172.16.4.193 /26
- 172.16.4.207 /27
Determining Subnet Network Address
Q: Which of the following processes is used by routers to determine the network address of the subnet based on an IP address and subnet mask given?
A: Binary AND operation
Subnet Mask for Maximum Hosts
Q: What subnet mask should a network administrator assign to a network address of 172.30.1.0 if it were possible to have up to 254 hosts?
A: 255.255.255.0
Identifying Private IP Addresses
Q: What are the three private IP addresses? (Choose three.)
- 10.35.66.70
- 192.168.99.5
- 172.18.88.90
Describing an IP Address
Q: Given the IP address and subnet mask of 172.16.134.64/27, which of the following would describe this address?
A: This is a network address.
Determining Subnet IP Address
Q: At a router interface is assigned an IP address of 172.16.192.166 with a mask of 255.255.255.248. What subnet IP address does it belong to?
A: 172.16.192.160
Subnet Configuration for a Workgroup Server
Q: Refer to the exhibit (not provided). The network administrator has assigned the internetwork of LBMISS an address range of 192.168.10.0. This address range has been divided into subnets using a mask /29. In order to equip a new building, the technician has decided to use the fifth subnet for configuring the new network (the first subnet is subnet zero). According to company policy, the router interface is always assigned the first usable host address, and the workgroup server is given the last usable host address. Which of the following settings should be entered in the server properties of the working group to enable connectivity to the network?
A: Provide the specific IP address, subnet mask, and default gateway based on the subnet calculations.
Devices Requiring Static IP Addresses
Q: Which of the following network devices are recommended to assign static IP addresses? (Choose three.)
- Servers
- Network Printers
- Routers
Features of IPv6
Q: Which of the following are features of IPv6? (Choose three.)
- Increased address space
- Data types and classes of service
- Authentication and encryption
Reason for IPv6 Development
Q: What is the main reason for the development of IPv6?
A: Expanded addressing capabilities
Router Behavior with TTL Value of 1
Q: What two things will happen if a router receives an ICMP packet that has a value of TTL (Time To Live) of 1 and the destination host is several hops away? (Choose two.)
- The router will discard the packet.
- The router will send a Time Exceeded message to the source host.
Interpreting Ping Response
Q: Refer to the exhibit (not provided). Why show the response after issuing the command ping 127.0.0.1 on a PC?
A: Provide the specific response shown in the exhibit. If the response indicates an error, it could suggest an issue with the TCP/IP stack configuration on the host.
Number of Bits in IPv4 Address
Q: How many bits make up an IPv4 address?
A: 32
Troubleshooting Internet Connectivity
Q: Refer to the exhibit (not provided). A network administrator discovers that host A has issues with Internet connectivity, but the server farm has full connectivity. In addition, host A has full connectivity to the server farm. What is the source of the problem?
A: Provide a more specific answer based on the exhibit. A possible issue could be the lack of Network Address Translation (NAT) configured on the router for host A’s network.
Truths about IPv4 Network Portion
Q: What are the three truths about the network portion of an IPv4 address? (Choose three.)
- It is identical for all hosts in a broadcast domain.
- It varies in length depending on the subnet mask.
- It is used by routers to forward packets.
Group of Hosts with Identical High-Order Bits
Q: What do we call a group of hosts that have identical bit patterns in the high-order bits of their addresses?
A: A network or subnet
Network Address in Binary
Q: What is the network address of the host 172.25.67.99/23 in binary?
A: 10101100.00011001.01000010.00000000
Determining Adequate Subnet Mask
Q: Refer to the exhibit (not provided). A network administrator must develop an addressing scheme for IP address space using 192.168.1.0/24. They have already dedicated the network that contains the serial link to a separate range. Each remaining network is assigned the same number of host addresses. What netmask must be adequate to address the other networks?
A: Provide the specific subnet mask based on the number of remaining networks and required host addresses per network.
Chapter 7: Data Link Layer Concepts
Factors for Implementing a Layer 2 Protocol
Q: What are the three factors to be taken into account when implementing a Layer 2 protocol in a network? (Choose three.)
- The geographical scope of the network
- The physical layer implementation (cabling, connectors, etc.)
- The number of hosts that will be connected
Identifying Destination MAC Address
Q: Refer to the exhibit (not provided). Assuming that the network is converged, meaning that the routing tables and ARP tables are complete, which of the following MAC addresses should be placed in the destination address field of Ethernet frames destined for www.server?
A: Provide the specific MAC address based on the exhibit. This likely requires information from an ARP table or similar.
Properties of Contention-Based Media Access
Q: What options are properties of access to media based in contention for shared media? (Choose three.)
- Non-deterministic (access is not guaranteed)
- Less expensive (compared to deterministic methods)
- Collisions can occur
Logical vs. Physical Topologies
Q: What is true of physical and logical topologies?
A: Logical topologies represent the virtual connections between nodes, while physical topologies depict the actual physical layout of network devices and cabling.
Determining MAC Method
Q: What determines the method of the Media Access Control (MAC)? (Choose two.)
- Media sharing (shared vs. dedicated)
- Logical topology
Statements about Media Access Control
Q: What statements describe the logical topology token passing? (Choose two.)
- It enables computers to transmit data only when they possess a token.
- Electronic tokens are passed sequentially to each node.
Identifying Physical Topology Representation
Q: A network administrator has been requested to provide a graphical representation of the exact location in the building of network cabling and equipment of the company. What kind of picture is it?
A: Physical topology diagram
Statements about OSI Model Addresses
Q: Which of the following statements are true regarding addresses found at each layer of the OSI model? (Choose two.)
- Layer 2 identifies devices by a physical address (MAC address) recorded on the network interface card.
- Layer 3 uses a hierarchical addressing scheme (IP addresses).
Identifying Media Access Control Methods
Q: Refer to the exhibit (not provided). Which statement describes the methods of medium access control using networks in the presentation?
A: Provide the specific media access control methods (e.g., CSMA/CD, CSMA/CA, token passing) used by each network shown in the exhibit.
Counting CRC Calculations
Q: Refer to the exhibit (not provided). How many unique CRC calculations will take place when traffic is routed from PC to the laptop?
A: Provide the specific number of CRC calculations based on the number of network segments and devices involved in the path.
Identifying IP and MAC Addresses in a Frame
Q: Refer to the exhibit (not provided). A frame is sent from the PC to the laptop. What destination IP addresses and MAC addresses will be included in the frame as part of RouterB? (Choose two.)
A: Provide the specific source and destination IP and MAC addresses based on the routing path and MAC address tables.
Data Link Layer Sublayer for Signal Preparation
Q: What sublayer of the data link layer prepares a signal to be transmitted at the physical layer?
A: Media Access Control (MAC) sublayer
Statements about Device Moving Networks
Q: Which statements are true when a device moves from one network or subnet to another? (Choose two.)
- The device will retain its MAC address as it operates at Layer 2.
- The device will need a new IP address assigned to communicate on the new network.
Function of the Data Link Layer
Q: What is a function of the data link layer?
A: It provides data transfer and error detection across a shared local media.
Characteristic of Logical Point-to-Point Topology
Q: What is a characteristic of a logical point-to-point topology?
A: The media access control protocol can be very simple as only two devices communicate directly.
Purpose of Packet Encapsulation into Frames
Q: What is one of the main purposes of encapsulation of packets into frames?
A: It facilitates the easy entry and exit of data onto the media and provides addressing and error detection information.
Purpose of Trailer in Data Link Layer Frame
Q: What is the main purpose of the trailer in a data link layer frame?
A: It typically contains a frame check sequence (FCS) or cyclic redundancy check (CRC) to allow for error detection in the frame.
Characteristics of Valid Ethernet Addresses
Q: What are the three characteristics of valid addresses for Layer 2 Ethernet? (Choose three.)
- They have a length of 48 bits.
- They are considered physical addresses (MAC addresses).
- They are usually represented in hexadecimal format.