Comprehensive CCNA Study Notes: Cisco IOS Access, Protocols and Models, and Physical Layer Infrastructure

Chapter 2: Basic Switch and End Device Configuration

Cisco IOS Access

Operating System Architecture:
- Kernel: The portion of the operating system that directly communicates with computer hardware and manages hardware resources to meet software requirements.
- Shell: The user interface that allows users to request specific tasks from the computer, interfacing between applications/users and the kernel. Interacted with via CLI or GUI.
- Hardware: The physical part of a computer, including underlying electronics.
Command-Line Interface (CLI) vs. Graphical User Interface (GUI):
- CLI: Text-based environment where commands are entered on a keyboard at a command prompt. It requires low system overhead, provides precise control, and is highly stable. However, it requires user knowledge of command structures.
- GUI: Environment utilizing graphical icons, menus, and windows (e.g., Windows 10, macOS, Linux KDE, Apple iOS, Android). It is user-friendly but resource-intensive and prone to crashes or functionality limitations.
Cisco Network Operating Systems:
- Cisco IOS (Internetwork Operating System): The primary family of network operating systems used on Cisco routers and switches. Specific hardware types utilize dedicated IOS releases.
- Other Cisco Operating Systems: IOS XE, IOS XR, and NX-OS.
- Home Routers: Operating systems on home network routers are generally referred to as firmware, typically configured via a web browser GUI.
Device Access Methods:
- Console: A physical management port providing out-of-band access to a Cisco device. Out-of-band access uses a dedicated management channel solely for device maintenance without requiring active network services. Requires terminal emulation software and a specialized console cable.
- Secure Shell (SSH): An in-band, recommended method for remotely establishing a secure CLI connection over a network interface. Requires active network services and configured IP addresses. IOS includes an SSH server and client.
- Telnet: An insecure, in-band method for remote CLI access over a network interface. Transmits authentication credentials and commands in plaintext. Recommended for lab environments only.
- Auxiliary (AUX) Port: A legacy out-of-band physical port found on routers, used for remote CLI management over a telephone line using a modem.
Terminal Emulation Software:
- Programs used to connect to network devices via serial console or SSH/Telnet include PuTTY, Tera Term, and SecureCRT.

IOS Navigation

Primary Command Modes:
- User EXEC Mode: View-only mode with limited basic monitoring commands. Cannot make configuration changes. Identified by prompt ending with > (e.g., Switch>).
- Privileged EXEC Mode: Provides full access to all monitoring, management, and configuration commands. Identified by prompt ending with # (e.g., Switch#). Also referred to as enable mode.
Configuration and Subconfiguration Modes:
- Global Configuration Mode: Accessed from privileged EXEC mode to make configuration changes affecting device-wide operation. Prompt format: Switch(config)#.
- Line Configuration Mode: Subconfiguration mode used to configure console, SSH, Telnet, or AUX access. Prompt format: Switch(config-line)#.
- Interface Configuration Mode: Subconfiguration mode used to configure specific network ports or switch virtual interfaces. Prompt format: Switch(config-if)#.
IOS Navigation Commands:
- enable: Moves from User EXEC mode to Privileged EXEC mode.
- disable: Moves from Privileged EXEC mode back to User EXEC mode.
- configure terminal: Moves from Privileged EXEC mode to Global Configuration mode.
- exit: Moves back one step in the configuration hierarchy (e.g., from subconfiguration mode to global configuration mode, or global configuration mode to privileged EXEC mode).
- end or key combination Ctrl+Z: Exits any subconfiguration mode directly back to Privileged EXEC mode.
- line console 0: Enters line subconfiguration mode for the console port.
- interface FastEthernet 0/1: Direct navigation from one subconfiguration mode to another interface subconfiguration mode.

The Cisco IOS Command Structure

Command Syntax Structure:
- Format: Prompt Command Space Keyword or Argument.
- Keyword: A specific, predefined parameter defined in the operating system (e.g., ip protocols).
- Argument: A non-predefined variable supplied by the user (e.g., IP address 192.168.10.5).
Command Syntax Conventions:
- Boldface: Commands and keywords entered literally as shown.
- Italics: Arguments for which the user supplies values.
- [x]: Indicates an optional element.
- {x}: Indicates a required element.
- [{x | y}]: Indicates a required choice within an optional element.
IOS Help Features:
- Context-Sensitive Help: Entered by typing ? at the prompt. Displays available commands in current mode, commands matching specific character prefixes, or keywords/arguments required for a command.
- Command Syntax Check: Command interpreter evaluates entries left to right. Returns feedback upon encountering invalid, incomplete, or ambiguous input.
CLI Hot Keys and Shortcuts:
- Tab: Completes partial command or keyword entry.
- Backspace: Erases character to left of cursor.
- Ctrl+D: Erases character at cursor.
- Ctrl+K: Erases characters from cursor to end of line.
- Esc+D: Erases characters from cursor to end of word.
- Ctrl+U or Ctrl+X: Erases all characters from cursor back to line start.
- Ctrl+W: Erases word to left of cursor.
- Ctrl+A: Moves cursor to line start.
- Left Arrow or Ctrl+B: Moves cursor one character left.
- Esc+B: Moves cursor back one word left.
- Esc+F: Moves cursor forward one word right.
- Right Arrow or Ctrl+F: Moves cursor one character right.
- Ctrl+E: Moves cursor to end of line.
- Up Arrow or Ctrl+P: Recalls previous commands in history buffer.
- Ctrl+R, Ctrl+I, or Ctrl+L: Redisplays prompt and command line after receiving console messages.
- --More-- Prompt Shortcuts: Enter key displays next line; Spacebar displays next screen; any other key cancels display.
- Break Key Sequences: Ctrl+C cancels current entry/command; Ctrl+Z exits configuration mode; Ctrl+Shift+6 all-purpose break sequence (aborts DNS lookups, pings, traceroutes).

Basic Device Configuration

Device Naming Guidelines:
- Hostnames must start with a letter, contain no spaces, end with a letter or digit, use only letters, digits, and dashes, and be fewer than $64\,\text{characters}$ in length.
- Hostname configuration command: hostname <Name> inside global configuration mode.
- Revert hostname command: no hostname.
Securing Device Access:
- User EXEC Console Password:
- Sw-Floor-1(config)# line console 0
- Sw-Floor-1(config-line)# password cisco
- Sw-Floor-1(config-line)# login
- Privileged EXEC Secret Password:
- Sw-Floor-1(config)# enable secret class
- Virtual Terminal (VTY) Remote Access Lines (Supports up to $16\,\text{lines}$ , numbered $0$ to $15$ ):
- Sw-Floor-1(config)# line vty 0 15
- Sw-Floor-1(config-line)# password cisco
- Sw-Floor-1(config-line)# login
- Encrypting Plaintext Passwords:
- Sw-Floor-1(config)# service password-encryption
- Converts plaintext passwords into weak encrypted strings in configuration files (show running-config).
Banner Messages:
- Declares authorized access boundaries for legal compliance.
- Command: banner motd # Authorized Access Only # (where # is a unique delimiting character not present inside the message text).

Saving Configurations

System Configuration Files:
- running-config: Active working file stored in volatile Random-Access Memory (RAM). Lost on reboot/power outage. Viewed with show running-config.
- startup-config: Saved configuration file stored in Non-Volatile Random-Access Memory (NVRAM) or Flash (config.txt on switches). Retained on reboot. Viewed with show startup-config.
Configuration Management Commands:
- Save active memory changes: copy running-config startup-config
- Clear startup configuration: erase startup-config
- Restart device: reload
Capturing Configuration to Text File:
1. Connect via terminal emulator (e.g., PuTTY).
2. Enable session logging to capture output to file (e.g., MySwitchLogs).
3. Execute show running-config or show startup-config in Privileged EXEC mode.
4. Disable session logging.
5. Restore configuration by entering Global Configuration mode and pasting saved log text into terminal.

Ports, Addressing, and Connectivity

IP Addressing Principles:
- IPv4 Address: $32\,\text{bits}$ written in dotted-decimal notation (four octets from $0$ to $255$ ).
- IPv4 Subnet Mask: $32\,\text{bits}$ defining the boundary between network portion and host portion.
- Default Gateway: IP address of the local router interface enabling access to remote networks.
- IPv6 Address: $128\,\text{bits}$ written as hexadecimal values grouped in four-digit blocks separated by colons.
Network Interfaces and Media:
- Physical Layer media types: Copper cables, Fiber-optic cables, Wireless.
- Switch Virtual Interface (SVI): Logical Layer 3 software interface on Layer 2 switches (default interface: vlan 1) used for remote IP management access.
Configuring SVI on a Switch:
- Sw-Floor-1(config)# interface vlan 1
- Sw-Floor-1(config-if)# ip address 192.168.1.20 255.255.255.0
- Sw-Floor-1(config-if)# ip default-gateway 192.168.1.1
- Sw-Floor-1(config-if)# no shutdown
Verification Utilities:
- ipconfig: Command-line tool on Windows PCs to verify IP, subnet mask, and default gateway settings.
- show ip interface brief: Cisco IOS command displaying status, operational state, and IP addresses of physical/virtual interfaces.
- ping: Command utility testing end-to-end IP network connectivity.
- traceroute: Command utility tracing path packets take across network hops.

Chapter 3: Protocols and Models

Fundamentals of Communication and Rules

Core Elements of Communication:
- Message Source (Sender): Person or device originating the message.
- Message Destination (Receiver): Receiving entity that interprets the message.
- Channel: Physical or logical medium providing path for message transmission.
Protocol Requirements for Network Communication:
- Encoding: Process of converting information into an acceptable signal form for transmission. Decoding reverses this process at destination.
- Formatting and Encapsulation: Structuring data according to standard frame patterns (e.g., envelope addressing fields enclosing letter content).
- Message Size: Segmenting long data streams into smaller individual frames meeting length bounds.
- Message Timing:
- Flow Control: Managing transmission rate between sender and receiver.
- Response Timeout: Duration host waits for response before taking corrective action.
- Access Method: Rules governing when a device can transmit over media (e.g., collision handling on shared media).
- Message Delivery Options:
- Unicast: One-to-one transmission to a single destination.
- Multicast: One-to-many transmission to specific host group.
- Broadcast: One-to-all transmission to all nodes on local network.

Protocols and Functions

Types of Network Protocols:
- Network Communications: Ethernet, IP, TCP, HTTP.
- Network Security: SSH, SSL, TLS.
- Routing Protocols: OSPF, BGP.
- Service Discovery: DHCP, DNS.
Protocol Functions:
- Addressing: Identifies source and destination endpoints (Ethernet, IPv4, IPv6).
- Reliability: Ensures guaranteed delivery mechanisms (TCP).
- Flow Control: Regulates data transfer rates (TCP).
- Sequencing: Labels segments with sequence numbers for ordered reassembly (TCP).
- Error Detection: Verifies checksum integrity against corruption (Ethernet, IPv4, IPv6, TCP).
- Application Interface: Process-to-process communication for web/file access (HTTP, HTTPS).

Protocol Suites

Definition: A group of interrelated protocols working together to fulfill network communication services.
Evolution of Major Protocol Suites:
- TCP/IP: Dominant open standard protocol suite maintained by IETF.
- OSI Protocols: Developed jointly by ISO and ITU in 1977; mainly replaced by TCP/IP, though OSI model remains key conceptual framework.
- AppleTalk: Proprietary Apple protocol suite released in 1985; replaced by TCP/IP in 1995.
- Novell NetWare: Proprietary suite using IPX protocol released in 1983; replaced by TCP/IP in 1995.
TCP/IP Protocol Suite Details:
- Application Layer:
- Name System: DNS.
- Host Configuration: DHCPv4, DHCPv6, SLAAC.
- Email: SMTP, POP3, IMAP.
- File Transfer: FTP, SFTP, TFTP.
- Web and Web Service: HTTP, HTTPS, REST.
- Transport Layer:
- Connection-Oriented: TCP (acknowledged, reliable delivery).
- Connectionless: UDP (unacknowledged, fast best-effort delivery).
- Internet Layer:
- IP Protocols: IPv4 ( $32\,\text{bit}$ ), IPv6 ( $128\,\text{bit}$ ), NAT.
- Messaging: ICMPv4, ICMPv6, ICMPv6 ND.
- Routing: OSPF, EIGRP, BGP.
- Network Access Layer:
- Address Resolution: ARP.
- Data Link Protocols: Ethernet, WLAN (Wi-Fi).

Standards Organizations

Open Standards: Vendor-neutral specifications guaranteeing competition, interoperability, and market fairness.
Internet Governance Standards Bodies:
- Internet Society (ISOC): Promotes open internet development worldwide.
- Internet Architecture Board (IAB): Manages overall internet standards design.
- Internet Engineering Task Force (IETF): Develops and maintains TCP/IP technologies via Requests for Comments (RFC) documents.
- Internet Research Task Force (IRTF): Focuses on long-term research (ASRG, CFRG, P2PRG).
- ICANN: Coordinates IP address allocation and domain name structure.
- IANA: Managed under ICANN to allocate IP addresses, domain names, and TCP/UDP port numbers.
Electronic and Communications Standards Bodies:
- IEEE: Institute of Electrical and Electronics Engineers (defines 802.3 Ethernet and 802.11 WLAN).
- EIA: Electronic Industries Alliance (defines wiring, connectors, and 19-inch equipment racks).
- TIA: Telecommunications Industry Association (defines radio, cellular, VoIP, and satellite standards).
- ITU-T: International Telecommunication Union (defines video compression, IPTV, and DSL broadband).

Reference Models

Benefits of Layered Models: Modularizes network functions, assists protocol design, prevents changes in one layer from impacting others, fosters competition, establishes standard terminology.
OSI Reference Model ( $7\,\text{Layers}$ ):
- Layer 7 - Application: Process-to-process application interfaces.
- Layer 6 - Presentation: Common data formatting, representation, and encryption.
- Layer 5 - Session: Manages dialogues and data exchanges between applications.
- Layer 4 - Transport: Segmentation, transfer, flow control, and reassembly between endpoints.
- Layer 3 - Network: End-to-end logical addressing (IP) and routing.
- Layer 2 - Data Link: Node-to-node physical media access, frame formatting, MAC addressing.
- Layer 1 - Physical: Electrical, optical, or radio transmission of raw binary bits.
TCP/IP Protocol Model ( $4\,\text{Layers}$ ):
- Layer 4 - Application: Represents data, handles encoding and dialog control (Maps to OSI L5, L6, L7).
- Layer 3 - Transport: Supports cross-network end-to-end communication (Maps to OSI L4).
- Layer 2 - Internet: Determines best path through networks (Maps to OSI L3).
- Layer 1 - Network Access: Controls hardware devices and media (Maps to OSI L1, L2).

Data Encapsulation Principles

Segmentation and Multiplexing:
- Segmentation: Process of dividing data streams into smaller blocks for network transmission.
- Multiplexing: Interleaving separate segmented data streams across a shared communication medium.
- Benefits: Increases transmission speed, prevents single streams from monopolizing links, improves error recovery efficiency.
Protocol Data Units (PDUs):
- Application Layer: Data
- Transport Layer: Segment (TCP) or Datagram (UDP)
- Network Layer: Packet
- Data Link Layer: Frame
- Physical Layer: Bits
Encapsulation & De-encapsulation:
- Encapsulation: Top-down movement where higher-layer PDUs are wrapped inside lower-layer headers/trailers.
- De-encapsulation: Bottom-up processing at receiving endpoint where protocol headers are analyzed and stripped layer-by-layer.

Data Access and Addressing

Layer 3 Logical Addressing:
- Source & Destination IP Addresses.
- IP Address Structure: Network Portion/Prefix + Host Portion/Interface ID.
- Delivers packets from original source to final destination across logical networks.
Layer 2 Physical Addressing:
- Source & Destination MAC Addresses ( $48\,\text{bits}$ written in hexadecimal).
- Delivers frames locally from NIC to NIC on same physical network link.
Addressing Scenarios:
- Communication on Same Local Network:
- Destination IP = Destination Host IP.
- Destination MAC = Destination Host MAC address.
- Communication on Remote Network:
- Destination IP = Final Remote Host IP.
- Destination MAC = Local Default Gateway (Router) MAC address.
- Wireshark: Software protocol analyzer ("packet sniffer") used to capture and inspect real-time packet headers and data link frames.

Chapter 4: Physical Layer

Purpose and Characteristics of the Physical Layer

Function: Accepts complete data link layer frames and encodes them into electrical, optical, or radio wave signals transmitted onto physical media.
Physical Network Connections:
- Wired Connections: Uses physical cabling (copper or fiber) connected to a Network Interface Card (NIC) or switch port.
- Wireless Connections: Transmits data using radio waves via Wireless Access Points (APs) or wireless routers to WLAN NICs.
Physical Layer Standards Organizations:
- Standards defined in hardware by ISO, TIA/EIA, ITU, ANSI, IEEE, FCC, and ETSI.
Functional Areas of Physical Layer Standards:
- Physical Components: Connectors, media, pinouts, electronic circuitry, interfaces.
- Encoding: Line encoding patterns representing bit streams (e.g., Manchester encoding where high-to-low transition is $0$ bit and low-to-high is $1$ bit; used in $10\,\text{Mbps}$ Ethernet 10BASE-TX. 100BASE-TX uses 4B/5B; 1000BASE-T uses 8B/10B).
- Signaling: Method of generating physical signals (voltage levels, light pulses, RF microwaves) representing binary $1$ s and $0$ s.
Bandwidth Metrics and Units:
- Bandwidth: Capacity of a medium to carry data over time.
- Units:
- $1\,\text{bps} = \text{fundamental unit of bandwidth}$
- $1\,\text{Kbps} = 1000\,\text{bps} = 10^{3}\,\text{bps}$
- $1\,\text{Mbps} = 1,000,000\,\text{bps} = 10^{6}\,\text{bps}$
- $1\,\text{Gbps} = 1,000,000,000\,\text{bps} = 10^{9}\,\text{bps}$
- $1\,\text{Tbps} = 1,000,000,000,000\,\text{bps} = 10^{12}\,\text{bps}$
- Latency: Total time delay for data to travel from origin point to destination.
- Throughput: Actual transfer rate of bits across media over a given period (impacted by traffic volume, traffic type, and intermediate latency).
- Goodput: Measure of usable data transferred over a given period.
- Equation: $\text{Goodput} = \text{Throughput} - \text{Protocol Overhead}$

Copper Cabling

Characteristics: Inexpensive, easy to install, low electrical resistance; limited by signal attenuation over distance and susceptibility to interference.
Sources of Signal Interference:
- Electromagnetic Interference (EMI) & Radio Frequency Interference (RFI): Distortion caused by fluorescent lighting, motors, or radio waves.
- Crosstalk: Signal disturbance caused by magnetic fields of one wire interfering with adjacent wire signals.
Types of Copper Cabling:
- Unshielded Twisted-Pair (UTP): Four color-coded wire pairs encased in plastic jacket. Relies on wire cancellation and varying pair twist rates to counter crosstalk.
- Shielded Twisted-Pair (STP): Provides superior noise protection. Incorporates individual pair foil shielding plus overall braided metallic foil shield. Requires specialized grounded STP connectors.
- Coaxial Cable: Single central copper conductor surrounded by flexible plastic insulation, woven copper braid/foil shielding, and outer cable jacket. Connectors: BNC, N-type, F-type. Used for wireless antennas and cable TV/internet installations.

UTP Standards and Pinouts

Standards Body: TIA/EIA-568 governs commercial LAN cabling standards (cable types, lengths, connectors, terminations, testing).
UTP Cable Categories:
- Category 3: Voice communication.
- Category 5: Supports speeds up to $100\,\text{Mbps}$ .
- Category 5e: Enhanced capability supporting $1000\,\text{Mbps}$ ( $1\,\text{Gbps}$ ); baseline standard for new installs.
- Category 6: Added internal pair separator supporting up to $10\,\text{Gbps}$ .
- Category 6a: Improved crosstalk features for $10\,\text{Gbps}$ over extended distances.
- Category 7: Supports $10\,\text{Gbps}$ .
- Category 8: Supports $40\,\text{Gbps}$ .
UTP Connectors: RJ-45 male plugs crimped on cable ends; RJ-45 female sockets on devices, wall jacks, and patch panels.
Wiring Conventions & Types:
- Ethernet Straight-Through: Both ends terminated using T568A or T568B. Connects host to switch or switch to router.
- Ethernet Crossover: One end T568A, other end T568B. Connects like devices (switch to switch, router to router, host to host). Auto-MDIX feature automatically detects cable types on modern interfaces.
- Rollover: Cisco proprietary cable connecting host serial port to router/switch console port.
Color Code Pinouts:
- T568A Standard:
- Pin 1: Green-White
- Pin 2: Green
- Pin 3: Orange-White
- Pin 4: Blue
- Pin 5: Blue-White
- Pin 6: Orange
- Pin 7: Brown-White
- Pin 8: Brown
- T568B Standard:
- Pin 1: Orange-White
- Pin 2: Orange
- Pin 3: Green-White
- Pin 4: Blue
- Pin 5: Blue-White
- Pin 6: Green
- Pin 7: Brown-White
- Pin 8: Brown

Fiber-Optic Cabling

Characteristics: Transmits encoded light impulses across pure glass strands; supports long distances ( $1\,\text{m}$ to $100,000\,\text{m}$ ) and high bandwidth ( $10\,\text{Mbps}$ to $100\,\text{Gbps}$ ); completely immune to EMI, RFI, and electrical hazards.
Fiber Cable Types:
- Single-Mode Fiber (SMF): Very small core ( $9\,\text{microns}$ ); uses expensive lasers; single light path; zero dispersion; used for long haul ( $100+\text{ km}$ ). Yellow outer jacket.
- Multi-Mode Fiber (MMF): Larger core ( $50\,\text{microns}$ or $62.5\,\text{microns}$ ); uses inexpensive LEDs; multiple light paths; susceptible to light dispersion; limited distance up to $550\,\text{meters}$ at $10\,\text{Gbps}$ . Orange or aqua jacket.
Fiber-Optic Connectors:
- Straight-Tip (ST): Twist-on bayonet lock.
- Subscriber Connector (SC): Square push-pull latching mechanism.
- Lucent Connector (LC): Small form-factor simplex/duplex connector.
- Small Form-Factor Pluggable (SFP): Transceiver module interface on routers/switches.
Comparison: UTP vs. Fiber-Optic Cabling:
- Bandwidth: UTP ( $10\,\text{Mbps}$ to $10\,\text{Gbps}$ ) vs. Fiber ( $10\,\text{Mbps}$ to $100\,\text{Gbps}$ ).
- Distance: UTP ( $1\,\text{m}$ to $100\,\text{m}$ ) vs. Fiber ( $1\,\text{m}$ to $100,000\,\text{m}$ ).
- Immunity to EMI/RFI & Electrical Hazards: UTP is Low; Fiber is High (completely immune).
- Media/Connector Cost & Installation Skills: UTP is Lowest; Fiber is Highest.

Wireless Media

Characteristics: Carries electromagnetic signals across radio frequencies; offers maximum endpoint mobility. Limitations include limited coverage area, susceptibility to RF interference (microwaves, cordless phones, fluorescent lights), security risks, and half-duplex shared medium dynamics.
Wireless Standards:
- Wi-Fi (IEEE 802.11): WLAN technology using CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance).
- Bluetooth (IEEE 802.15): WPAN standard operating across $1\,\text{m}$ to $100\,\text{m}$ device pairings.
- WiMAX (IEEE 802.16): Point-to-multipoint broadband wireless standard.
- Zigbee (IEEE 802.15.4): Low data rate, low power, short range protocol used in IoT environments.
WLAN Devices: Wireless Access Points (APs) and Wireless NIC adapters.

Review Questions and Detailed Answers

Chapter 2 Review Questions

Which statement is true about the running configuration file in a Cisco IOS device?
- Answer: It affects the operation of the device immediately when modified.
Which two statements are true regarding user EXEC mode?
- Answer: The device prompt for this mode ends with the > symbol; Only some aspects of the router configuration can be viewed.
Which type of access is secured on a Cisco router or switch with the enable secret command?
- Answer: privileged EXEC
What is the default SVI on a Cisco switch?
- Answer: VLAN 1
When a hostname is configured through the Cisco CLI, which three naming conventions are part of the guidelines?
- Answer: The hostname should be fewer than $64\,\text{characters}$ in length; The hostname should contain no spaces; The hostname should begin with a letter.
What is the function of the shell in an OS?
- Answer: It interfaces between the users and the kernel.
A switch with a valid operating system contains a configuration file stored in NVRAM. The configuration file has an enable secret password but no line console 0 password. When the router boots up, which mode will display?
- Answer: user EXEC mode
An administrator has just changed the IP address of an interface on an IOS device. What else must be done in order to apply those changes to the device?
- Answer: Nothing must be done. Changes to the configuration on an IOS device take effect as soon as the command is typed correctly and the Enter key has been pressed.
Which memory location on a Cisco router or switch loses all content when the device is restarted?
- Answer: RAM
Why would a technician enter the command copy startup-config running-config?
- Answer: to copy an existing configuration into RAM
Which functionality is provided by DHCP?
- Answer: automatic assignment of an IP address to each host
Which two functions are provided to users by the context-sensitive help feature of the Cisco IOS CLI?
- Answer: displaying a list of all commands available in the current mode; determining which option, keyword, or argument is available for the entered command
Which memory location on a Cisco router stores the startup configuration file?
- Answer: NVRAM

Chapter 3 Review Questions

Which of the following are standards organizations?
- Answer: IANA, IEEE, IETF
What type of communication sends a message to all devices on a local area network?
- Answer: broadcast
In computer communication, what is the purpose of message encoding?
- Answer: to convert information to the appropriate form for transmission
Which message delivery option is used when all devices need to receive the same message simultaneously?
- Answer: broadcast
What are two benefits of using a layered network model?
- Answer: It assists in protocol design; It prevents technology in one layer from affecting other layers.
What is the purpose of protocols in data communications?
- Answer: providing the rules required for a specific type of communication to occur
Which logical address is used for delivery of data to a remote network?
- Answer: destination IP address
What is the general term that is used to describe a piece of data at any layer of a networking model?
- Answer: protocol data unit
Which two protocols function at the internet layer?
- Answer: ICMP, IP
Which layer of the OSI model defines services to segment and reassemble data for individual communications between end devices?
- Answer: transport
Which type of communication sends a message to a group of host destinations simultaneously?
- Answer: multicast
What process is used to receive transmitted data and convert it into a readable message?
- Answer: decoding
What is done to an IP packet before it is transmitted over the physical medium?
- Answer: It is encapsulated in a Layer 2 frame.
What process is used to place one message inside another message for transfer from a source to a destination?
- Answer: encapsulation
A web client is sending a request for a web page to a web server. From the perspective of the client, what is the correct order of the protocol stack that is used to prepare the request for transmission?
- Answer: HTTP, TCP, IP, Ethernet

Chapter 4 Review Questions

What is the purpose of the OSI physical layer?
- Answer: transmitting bits across the local media
Why are two strands of fiber used for a single fiber-optic connection?
- Answer: The two strands allow for full-duplex connectivity.
Which of the following describes crosstalk?
- Answer: the distortion of a transmitted message due to signals carried in adjacent wires
Which procedure is used to reduce the effect of crosstalk in copper cables?
- Answer: twisting opposing-circuit wire pairs together
Which type of UTP cable is used to connect a PC to a switch port?
- Answer: straight-through
What is the definition of bandwidth?
- Answer: the amount of data that can flow in a given amount of time
Which statement correctly describes frame encoding?
- Answer: It converts bits into a predefined code in order to provide a predictable pattern to help distinguish data bits from control bits.
Which of the following is a characteristic of UTP cabling?
- Answer: cancellation
A wireless LAN is being deployed inside the new one-room office that is occupied by the park ranger… After network testing is complete, the technicians report that the wireless LAN signal is occasionally affected by some type of interference. What is a possible cause of the signal distortion?
- Answer: the microwave oven
What is indicated by the term throughput?
- Answer: the measure of bits transferred across media over a given period of time
What is one advantage of using fiber-optic cabling rather than copper cabling?
- Answer: It is able to carry signals much farther than copper cabling.
Which standards organization oversees development of wireless LAN standards?
- Answer: IEEE
A network administrator is designing a new network infrastructure that includes both wired and wireless connectivity. In which situation would a wireless connection be recommended?
- Answer: The end-user device needs mobility when connecting to the network.
A network administrator is troubleshooting connectivity issues on a server. Using a tester, the administrator notices that the signals generated by the server NIC are distorted and not usable. In which layer of the OSI model does the error occur?
- Answer: physical layer
What type of cable is used to connect a workstation serial port to a Cisco router console port?
- Answer: rollover