Cisco Networking Fundamentals Flashcards
Intermediary devices / network devices
Devices used to transport data across the network.
Home routers are 4 devices in one:
- router
- switch
- wireless access point
- firewall
Cisco IOS
The Cisco Internetwork Operating System. A generic term for the collection of network operation systems used on Cisco networking devices. Cisco IOS is used for most Cisco devices.
Stored in a semi-permanent memory area called flash.
The kernel
The portion of the OS code that interacts directly with the computer hardware.
The shell
The portion of the OS that interfaces with the applications and the user. The kernel is between the shell and the hardware.
Major functions performed or enabled by Cisco routers:
- network security
- IP addressing of virtual and physical interfaces
- enabling network-specific configurations to optimize connectivity of their respective media
- routing
- enabling QoS
- network management
3 most common methods for accessing the CLI environment:
- console (cable)
- Telnet or SSH
- AUX port
Cisco IOS modes hierarchical structure:
Same for router or switch
- User executive mode - Router>
View-only mode - Privileged executive mode - Router#
- Global configuration mode - Router(config)#
Affects the whole device - other specific configuration modes
Like for a specific interface/engine/line
User EXEC mode
Allows a limited number of monitoring commands. View-only mode. Does not allows any commands that might change the device. Will need to set up a password.
Privileged EXEC mode
Allows configuration and management commands. Will need to set up a password. Must be here to access global configuration and all other modes.
Global configuration mode
The primary configuration mode. Must be here to get to the specific configuration modes.
CLI command to go from privileged EXEC to global configuration:
Switch# configure terminal
Interface mode
A specific configuration mode
To configure one of the network interfaces. (Fa0/0, S0/0/0)
Line mode
A specific configuration mode
To configure one of the physical or virtual lines (console, AUX, VTY)
To leave configuration mode completely and return to privileged EXEC:
end
To go from user exec to privileged exec:
enable
disable goes back to user exec
Entering “exit” in privileged exec:
Ends the console session.
CLI hot key: Ctrl-A
Moves to the beginning of the line.
CLI hot key: Ctrl-E
Moves to the end of the line.
CLI hot key: Ctrl-R
Redisplays a line.
CLI hot key: Ctrl-Z
Exits the configuration mode and goes back to privileged exec.
CLI hot key: Ctrl-C
Exits the configuration mode or aborts the current command. Cancels the current command and returns to privileged exec mode.
show interface
Displays statistics for all interfaces on the device. Add the slot/port number to see the stats for that particular one.
show startup-config
Displays the saved configuration located in NVRAM.
show running-config
Displays the contents of the currently running configuration file.
show version
Displays information about the currently loaded IOS version, along with hardware and device information.
IOS hostname
The name of the switch or router. Case sensitive. Must be in global configuration mode.
- start with a letter
- no spaces
- end with a letter or digit
- only letters, digits, and dashes
- less than 64 characters
Type: hostname whateverhostname
no hostname would remove the name of the device
enable password
Limits access to the privileged exec mode
enable secret
Encrypted, limits access to the privileged exec mode
console password
Limits devices access using the console connection. Must go into line configuration mode to set this password.
VTY password
Limits device access over Telnet. Must be in line configuration mode for that line to configure its password.
line console 0
Enters line configuration mode. Must be in global configuration mode first. The zero is the first (and usually only) console interface.
login
Use after setting a password so that it will ask for that password at login of that mode.
service-password-encryption
Prevents passwords from showing up as plaintext text when viewing the configuration files. Applies only to passwords in the configuration file, not as they are sent over the media.
banner motd
Message of the day banner. Follow this command with a space, a delimiting character, the message, another space, and then the delimiting character again.
copy running-config startup-config
Saves the running configuration file updates to the startup configuration file.
reload
In privileged exec
Restarts the device
Commands that will return the device to the default factory state:
erase startup-config
delete vlan.dat
(Must be in privileged exec)
Then reload the device and it will load the default startup configuration.
SVI
Switch virtual interface. Provides a means to remotely manage a switch over a network using IPv4. Each switch comes with one SVI in the default configuration: interface VLAN1.
interface vlan 1
Enters the interface configuration mode from the global configuration mode.
ip address whateveripaddressandsubnetmask sets the IP address and subnet mask. Must then run no shutdown to activate the interface.
show ip interface brief
Is like ipconfig for switches and routers. Verifies the interfaces of intermediary devices, showing IP addresses, state of each interface, etc.
CLI hot key: Ctrl-Shift-6
Allows the user to interrupt an IOS process such as ping or tracert.
Out-of-band access
Access via a dedicated management channel that is used for device maintenance purposes only.
Console port access
Using a console cable to plug directly in. Out-of-band access. By default, conveys the startup, debugging, and error messages.
Context-sensitive help
Provides a list of commands and the arguments associated with those commands within he context of the current mode. So, shows the commands available, and also shows which options, keywords, or arguments are matched with a specific command.
Encapsulation
The process of placing one message format inside another message format (like a letter in an envelope).
Segmenting
Breaking the message up into individual pieces that meet both the maximum and minimum requirements. Each segment is encapsulated in a separate frame.
Access method
Determines when someone is able to send a message. Let’s the computer know when to send a message and what to do about errors.
Flow control
Negotiates the timing for successful communication. The sending host can transmit faster than the destination can receive and process.
Response timeout
Rules that specify how long to wait for responses and what action to take if a response timeout occurs.
Unicast
One-to-one delivery option; a single destination for the message.
Multicast
One-to-many delivery option. The delivery of the same message to a group of host destinations simultaneously.
Broadcast
One-to-all delivery option. For when all the hosts on a network need to receive the message at the same time.
Protocol suite
A group of inter-related protocols necessary to perform a communication function.
Protocol stack
Shows how the individual protocols within a suite are implemented. The lower layers are conceded with moving data over the network and providing services to the upper layers, which are focused in the content of the message being sent.
HTTP
Hypertext Transfer Protocol. Governs the way a web server and a web client interact. HTTP defines the content and formatting of the requests and responses that are exchanged between the client and server. Both the client and the web server software implement HTTP as part of the application. HTTP relies on other protocols to govern how the messages are transported between the client and server.
Set of rules for exchanging text, graphic images, sound, video, and other multimedia files on the World Wide Web
A TCP/IP Application Layer protocol.
TCP
Transmission Control Protocol. Manages the individual conversations between web servers and web clients. TCP divides the HTTP messages into smaller pieces, called segments. These segments are sent between the web server and client processes running at the destination host. TCP is also responsible for controlling the size and rate at which messages are exchanged between the server and the client.
Enables reliable communication between processes running on separate hosts. Reliable, acknowledged transmissions that confirm successful delivery (as opposed to UDP).
A TCP/IP Transport Layer protocol.
IP
Internet Protocol. Responsible for taking the formatted segments from TCP, encapsulating them into packets, assigning them the appropriate addresses, and delivering them across the best path to the destination host.
A TCP/IP Internet Layer protocol.
TCP/IP model
or the Internet model
Application
Transport
Internet
Network Access
Defines the four categories of functions that must occur for communications to be successful.
DNS
Domain Name System/Service. Translates domain names into IP addresses.
TCP/IP Application Layer protocol
BOOTP
Bootstrap Protocol. Enables a diskless workstation to discover its own IP address, the IP address of a BOOTP server on the network, and a file to be loaded into memory to boot the machine. Now superseded by DHCP.
TCP/IP Application Layer protocol
DHCP
Dynamic Host Configuration Protocol. Dynamically assigns IP addresses to client stations at start-up and allows the addresses to be re-used when no longer needed.
TCP/IP Application Layer protocol
SMTP
Simple Mail Transfer Protocol. Enables clients to send email to a mail server and enables servers to send email to other servers.
TCP/IP Application Layer protocol
POP3
Post Office Protocol version 3. Enables clients to retrieve email from a mail server and downloads email from the mail server to the desktop.
TCP/IP Application Layer protocol
IMAP
Internet Message Access Protocol. Enables clients to access email stored on a mail server and maintains email on the server.
TCP/IP Application Layer protocol
FTP
File Transfer Protocol. Sets rules that enable a user on one host to access and transfer files to and from another host over a network. A reliable, connection-oriented, and acknowledged file delivery protocol.
TCP/IP Application Layer protocol
TFTP
Trivial File Transfer Protocol. A simple, connectionless file transfer protocol. A best-effort, unacknowledged file delivery protocol. Utilizes less overhead than FTP.
TCP/IP Application Layer protocol
UDP
User Datagram Protocol. Enables a process running on one host to send packets to a process running on another host. Does not confirm successful datagram transmission.
TCP/IP Transport Layer protocol
NAT
Network Address Translation. Translates IP addresses from a private network into globally unique public IP addresses.
TCP/IP Internet Layer protocol
ICMP
Internet Control Message Protocol. Provides feedback from a destination host to a source host about errors in packet delivery.
TCP/IP Internet Layer protocol
OSPF
Open Shortest Path First. Link-state routing protocol. Hierarchical design based on areas. Open standard interior routing protocol.
TCP/IP Internet Layer protocol
EIGRP
Enhanced Interior Gateway Routing Protocol. Cisco proprietary routing protocol. Uses composite metric based on bandwidth, delay, load and reliability.
TCP/IP Internet Layer protocol
ARP
Adress Resolution Protocol. Provides dynamic address mapping between an IP address and a hardware address.
Used by a sending host to discover the MAC address of any host on the same local network.
TCP/IP Network Access Layer protocol
PPP
Point-to-Point Protocol. Provides a means of encapsulating packets for transmission over a serial link.
TCP/IP Network Access Layer protocol
Ethernet
802.3 Defines the rules for wiring and signaling standards of the network access layer.
TCP/IP Network Access protocol.
Interface Drivers
Provides instruction to a machine for the control of a specific interface on a network device
TCP/IP Network Access Layer protocol
IP packet
When the data has been given its IP addressing information/header.
Data link frame
When the IP packet has been given its Ethernet information on both ends.
Wireless LAN
802.11
OSI Model
Application Presentation Session Transport Network Data Link Physical
OSI Layer 1
Physical.
The physical layer protocols describe the mechanical, electrical, functional, and procedural means to activate, maintain, and de-activate physical-connections for bit transmission to and from a network device.
OSI Layer 2
Data link.
The data link layer protocols describe methods for exchanging data frames between devices over a common media.
A Layer 2 physical address is used to deliver the data link frame from one network interface to another network interface on the same network. The data must be able to travel the physical medium before it can go across the network.
OSI Layer 3
Network.
The network layer provides services to exchange the individual pieces of data over the network between identified end devices. Provides a path or route.
A Layer 3 IP address has two parts, the network prefix and the host part. The network prefix is used by routers to forward the packet to the proper network. The host part is used by the last router in the path to deliver the packet to the destination device.
OSI Layer 4
Transport.
The transport layer defines services to segment, transfer, and reassemble the data for individual communications between the end devices.
OSI Layer 5
Session.
The session layer provides services to the presentation layer to organize its dialogue and to manage data exchange.
OSI Layer 6
Presentation.
The presentation layer provides for common representation of the data transferred between application layer services.
OSI Layer 7
Application.
The application layer provides the means for end-to-end connectivity between individuals in the human network using data networks.
TCP/IP Application Layer
Represents data to the user, plus encoding and dialog control. Organizes dialog - manages data exchange.
TCP/IP Transport Layer
Supports communication between diverse devices across diverse networks. Segments, transfers, and reassembles data.
TCP/IP Internet Layer
Determines the best path through the network.
TCP/IP Network Access Layer
Controls the hardware devices and media that make up the network. Exchanges frames between devices.
Segmentation
Breaking the message into smaller pieces for transmission. Allows different transmissions to be interleaved, taking turns sending their pieces (called multiplexing). Also increases reliability.
The encapsulation process / Data encapsulation
The process of adding various protocols and information to application data as it is passed down the protocol stack to be transmitted across the network media.
The process that adds additional protocol header information to the data before transmission.
PDUs
Protocol Data Unit. The form that a piece of data takes at any layer during encapsulation.
- Data - The general term for the PDU used at the application layer
- Segment - Transport layer PDU
- Packet - Network layer PUD
- Frame - Data link layer PDU
- Bits - A Physical layer PDU used when physically transmitting data over the medium
Default gateway
The IP address of an interface on a router on the same network as the sending host.
