Ccna Chapter 1

Front 1

UNICAST

Back 1

Communication from one host to one other host

Front 2

BROADCAST

Back 2

Communication from one host to all other hosts on the network

Front 3

MULTICAST

Back 3

Communication from one host to few hosts only

Front 4

4 Router Functions

Back 4

• Packet Switching
• Communication between networks
• Path Selection
• Packet Filtering

Front 5

Packet Switching

Back 5

Switching packets between networks

Front 6

Communication between networks

Back 6

Allow send/receive from connected networks

Front 7

Path Selection

Back 7

Ping all routers to find the best path to reach a given network

Front 8

Packet Filtering

Back 8

Drop or forward packets based on criteria (ex: source or destination)

Front 9

Local Area Network (LAN)

Back 9

A network covering a limited geographical area

• high data transfer rate
• (ex: floor, building, or campus)

Front 10

Wide Area Network (WAN)

Back 10

A network covering a large geographical area

• used to connect LAN\s across coverage area
• (ex: various office LANs connected by a WAN)

Front 11

Open Systems Interconnection (OSI)

Back 11

An open standard networking model published in 1984 by the International Organization for Standardization (ISO)

Front 12

TCP/IP model

Back 12

An open standard networking model developed by DARPA from 1973-1985.

TCP/IP eventually replace the OSI model

Front 13

OSI Application Layer (ALL)

Back 13

Provides a user interface

• Applications use the HTTP protocol to send/receive page requests and contents

Front 14

HTTP Protocol

Back 14

• Resides at the application layer
• Used by an application to get webpages from web servers across the network

Front 15

OSI Presentation Layer (PEOPLE)

Back 15

• Presents data to the Application Layer
• Handles encryption/decryption
• Translates data to/from the Application layer
• Data Compression/Decompression

Front 16

OSI Session Layer (SEEM)

Back 16

• Maintains distinction between data of separate application / sessions
• Provides dialog control between hosts
• Coordinates communication between systems

Front 17

OSI Transport Layer (TO)

Back 17

• Provides end-to-end connections
• Provides reliable or unreliable delivery
• Provides Flow Control
• Provides Error Recovery

Front 18

OSI Network Layer (NEED)

Back 18

• Provides Logical Addressing
• Provides Path determination using logical addressing

Front 19

Path Determination

Back 19

A router determines the best path to a destination address

Front 20

OSI Data Link Layer (DATA)

Back 20

• Provides data access and physical addressing
• Deals with data moving on the local network
• Defines protocols used to send/receive data across the media
• Switches function at this level

Front 21

OSI Physical Layer (Processing)

Back 21

• Converts digital data (to bits) so it can be sent over the physical medium
• Moves data between hosts
• Activates, Maintains, and Deactivates the physical link between systems (ex: switch & host)
• Connectors, cables, electrical currents etc.

Front 22

Header

Back 22

Contains control information related to the protocol being used at that layer

Front 23

Data Encapsulation

Back 23

The addition of a header to each layer in front of the data from the previous layer

Front 24

Protocol Data Unit (PDU)

Back 24

The header and data being send from one layer to the next lower layer

Front 25

Decapsulation

Back 25

Examining, processing, and removing the header

Front 26

OSI Layer Name Mnemonic

Back 26

• ALL -application
• PEOPLE - presentation
• SEEM - session
• TO - transport
• NEED - network
• DATA - data link
• PROCESSING - physical

Front 27

TCP/IP Application Layer

Back 27

• Various protocols that equate the OSI model's Application, Presentation, and Session layers
• interaction with the application
• data translation & encoding
• coordinating communication between systems

Front 28

Telnet Protocol

Back 28

• A terminal emulation protocol used to access the resources of a remote host
• usually provides access to the command line interface of the host

Front 29

HTTP Protocol

Back 29

• HyperText Transfer Protocol
• used to transfer webpages and resources from the Web Server to the Web Client

Front 30

FTP Protocol

Back 30

• File Transfer Protocol
• used for transferring files between two hosts

Front 31

TFTP Protocol

Back 31

• Trivial File Transfer Protocol
• only sends/receives files

Front 32

SMTP Protocol

Back 32

• Simple Mail Transfer Protocol
• used for sending email

Front 33

DNS Protocol

Back 33

• Domain Name Service
• helps map IP addresses of the host where a website originates/resides
• makes it easier to find resources on a network

Front 34

DCHP Protocol

Back 34

• Dynamic Host Configuration Protocol
• Automatically provides a host with an IP address
• Provides the address of the DNS server to resolve Names, Gateways, Subnet Masks, etc

Front 35

TCP/IP Transport Layer

Back 35

• End-toEnd transportation of data
• Sets up a logical connection between hosts

Front 36

Transmission Control Protocol (TCP)

Back 36

• Connection-oriented and reliable protocol
• Uses windowing to control flow
• provides ordered delivery of data in segments

Front 37

User Datagram Protocol (UDP)

Back 37

• simple data transfer without perks

Front 38

Well-Known Ports

Back 38

• Port numbers in the range of 1-1024

Front 39

Socket

Back 39

• Combination of IP address, Protocol (TCP or UDP), and Port Number

Front 40

HTTP Application Protocol

Back 40

• TCP Protocol
• Port 80

Front 41

HTTPS Application Protocol

Back 41

• TCP Protocol
• Port 443

Front 42

FTP (control) Application Protocol

Back 42

• TCP Protocol
• Port 21

Front 43

FTP (data) Application Protocol

Back 43

• TCP Protocol
• Port 20

Front 44

SSH Application Protocol

Back 44

• TCP Protocol
• Port 22

Front 45

Telnet Application Protocol

Back 45

• TCP Protocol
• Port 23

Front 46

DNS Application Protocol

Back 46

• TCP or UDP Protocol
• Port 53

Front 47

SMTP Application Protocol

Back 47

• TCP Protocol
• Port 25

Front 48

TFTP Application Protocol

Back 48

• UDP Protocol
• Port 69

Front 49

Three-Way Handshake (TCP)

Back 49

• Virtual Circuit between Source and Destination
• Uses SYN and ACK flags for sequencing data

Front 50

Maximum Transmission Unit (MTU)

Back 50

• Maximum amount of data that can be sent across a single Internet Layer PDU
• Limited by the Protocol used in that layer
• TCP breaks the data into segments each equal to the MTU

Front 51

Sliding Window (TCP)

Back 51

• Determines the number of segments that can be sent at a time
• The size of the window increases over time, but can be decreased by the destination host
• The source can only send the amount of segments designated by the window until it receives an ACK from the destination

Front 52

Reliable Delivery w/Error Recovery (TCP)

Back 52

• when the dest. receives the last segment in the window, it sends an ACK in the header to the source
• if the destination doesn't receive a segment, it does not send an acknowledgement back

Front 53

Ordered Delivery (TCP)

Back 53

• TCP transmits the data in the order received from the application layer
• Uses a sequence number to mark the order

Front 54

Sequence Number (TCP)

Back 54

• The source sequence number is the same as the previous ACK sent from the destination
• Used for ordering data if data is received in the wrong order to to network conditions

Front 55

Connection Termination (TCP)

Back 55

• Source sends a FIN flag and the destination responds with an ACK to close the session
• The source initiates a four-way handshake to close the session

Front 56

User Datagram Protocol (UDP)

Back 56

• Connectionless and unreliable protocol
• Delivers data without overheads
• good for voice and video to avoid delay

Front 57

UDP Header

Back 57

• Source Port
• Destination Port
• Length
• Checksum
• 8 bytes in size

Front 58

Internet Layer (UDP)

Back 58

• Corresponds to OSI Network Layer
• Ensures segments are moved across networks to the destination
• Provides logical addressing, path determination, and forwarding

Front 59

Internet Protocol (IP)

Back 59

• A logical address for each interface on a network (hosts, routers, switches, etc)

Front 60

Packet

Back 60

• A PDU (segment + header) including the source and destination IP addresses
• When a router receives a packet, the destination address tells the router where the packet should get forwarded

Front 61

Hop

Back 61

• Every time a packet goes through a router, it goes "one hop".
• Packets may have to travel multiple hops to reach its destination

Front 62

IPv4 Header

Front 63

IPv4 Header Length

Back 63

• minimum size of 20 bytes
• Most IPv4 headers are 20 bytes in length

Front 64

IPv4 Header Differentiated Services (DS) Field

Back 64

• Mark packets for priority depending on what kind of data they are carrying
• Data with no tolerance for delay (voice & video), are "marked up", while peer-to-peer traffic is "marked down"

Front 65

IPv4 Header Total Length Field

Back 65

The total size of the packet (header + data)

Front 66

IPv4 Header Identification Field

Back 66

• Segments may need to be broken into fragments before sending the data out
• Each fragment of a segment will have the same identification number

Front 67

IPv4 Header Flags Field

Back 67

Used in the fragmentation process

Front 68

IPv4 Header Fragmentation Offset

Back 68

Used by hosts to reassemble the data in the correct order

Front 69

IPv4 Header Time to Live (TTL) Field

Back 69

• Set at the originating host
• Passing through a router decreases TTL by 1
• If TTL reaches 0 before reaching the destination, the packet is dropped

Front 70

IPv4 Header Protocol Field

Back 70

Identifies the protocol to which the data belongs

Front 71

IPv4 Header Checksum Field

Back 71

• Used to check for errors in the header
• Each router performs a cyclic redundancy check on the header
• If the value does not match, the packet is discarded

Front 72

Cyclic Redundancy Check

Back 72

A test a router performs on a packet to check for errors in the packet header. A mismatched value results in discarding the packet

Front 73

IPv4 source IP address Field

Back 73

Stores the IP address of the packet's source

Front 74

IPv4 destination IP address Field

Back 74

Store the IP address of the packet's destination

Front 75

Routing Table

Back 75

• A table of all networks known by a router and all the routers in the internetwork
• Lists the next hop toward the destination
• Routers use routing protocols to build the Routing Table

Front 76

Internet Control Messaging Protocol (ICMP)

Back 76

• A management system and messaging service for IP
• Whenever IP encounters an error, it sends ICMP data as an IP packet

Front 77

"Destination Network Unreachable"

Back 77

A message generated by ICMP if the packet cannot be routed to the network in which the destination address resides

Front 78

"Time Exceeded"

Back 78

A message generated by ICMP if TTL expires to 0

Front 79

"Echo Reply"

Back 79

• When a source uses Ping to check network connectivity, the destination responds with and echo reply
• Successful receipt of an Echo Reply shows the destination host is reachable and available

Front 80

TCP Network Access Layer

Back 80

• Corresponds to the Data Link and Physical Layers of the OSI model
• Defines Protocols and Hardware required to connect a host to a physical network and deliver datas across it
• Limited to the physical layer boundary often defined by a layer 3 device (router)

Front 81

Frame

Back 81

• TCP Network Access Layer PDU
• contains the IP packet as well as a protocol header and trailer from the Net Access Layer`

Front 82

Ethernet

Back 82

A contention media access method that allows all hosts in a network to share the available bandwidth

Front 83

Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Protocol

Back 83

An ethernet protocol to resolve collision

• In the event of a collision, the host sends a jamming signal to notify all hosts
• Each host randomizes a timer and waits that random duration to resend the collided frame

Front 84

Half Duplex Logic

Back 84

A host can either send or receive at one time

• Hub-based networks use half-duplex to detect collisions

Front 85

Full Duplex Logic

Back 85

A host can send and receive data simultaneously

• Uses 2 pairs of wire instead of 1
• Switch-based networks use Full Duplex logic
• CSMA/CD is disabled at both ends

Front 86

Ethernet at the Data Link Layer

Back 86

Responsible for addressing and framing packets from the Network Layer and preparing them for transmission

Front 87

MAC address

Back 87

• Ethernet addressing used to identify a device or group of devices
• 48 bits (6 bytes) long
• written in hexadecimal format
• Each LAN interface card has a globally unique MAC address

Front 88

Unicast Address

Back 88

• Identifies a single device
• Used to identify the source and destination in a frame

Front 89

Organizationally Unique Identifyer (OUI)

Back 89

Each LAN card is assigned a code

• The first half of the MAC address is the OUI of the manufacturer assigned by the IEEE
• The second half is assigned by the manufacturer and is unique to the card

Front 90

Institute of Electrical and Electronics Engineers

(IEEE)

Back 90

Responsible for defining various electronics standards since 1980

Front 91

Broadcast Address

Back 91

A type of ethernet group address

• Has the value FFFF.FFFF.FFFF which means
• "all devices in the network process this frame"

Front 92

Multicast Address

Back 92

A type of ethernet group address

• Used when a frame needs to go to multiple hosts in the network
• the address 0100.5exx.xxxx is used where x can be any hexadecimal value

Front 93

Ethernet Framing

Back 93

Encapsulation of data from the Data Link layer into frames for transmission

Front 94

Preamble Field

Back 94

A Field on the Ethernet Frame

• 7 bytes in length
• Used for synchronization
• Tells the received data where the header starts

Front 95

Start Frame Delimiter (SFD) Field

Back 95

A Field on the Ethernet Frame

• 1 byte in length
• Tells the receiving device that the next byte is the destination address

Front 96

Destination Address Field

Back 96

A Field on the Ethernet Frame

• 6 bytes in length
• Identifies the intended destination of the frame

Front 97

Source Address Field

Back 97

A Field on the Ethernet Frame

• 6 bytes in length
• Identifies the source of the frame

Front 98

Length Field

Back 98

A Field on the Ethernet Frame

• 2 bytes in length (less than 0600 hex)
• Contains the length of the data field of the frame
• Field can be Length or Type but not both

Front 99

Type Field

Back 99

A Field on the Ethernet Frame

• 2 bytes in length (0600 hex or more)
• Identifies the Network Layer protocol whose data is contained in the frame
• Field can be Type or Length but not both

Front 100

Data Field

Back 100

A Field on the Ethernet Frame

• 45-1500 bytes in length
• The Network Layer Data

Front 101

FCS Field

Back 101

A Field on the Ethernet Frame

• 4 bytes in length
• Stores the CRC value used to check for errors in transmission

Front 102

Logical Link Control (LLC) Header

Back 102

• An IEEE 802.2 Header used on Headers using the Length Field
• Inserted after the Ethernet 802.3 header but before the Layer 3 header

Front 103

Subnetwork Access Protocol (SNAP) header

Back 103

• An IEEE 802.2 Header used on Headers using the Length Field
• Inserted after the Ethernet 802.3 header but before the Layer 3 header

Front 104

Ethernet 802.3 Standard

Back 104

• 10Mbps co-axial cable (Ethernet)
• 802.3u (FastEthernet)
• 802.3ab (Gigabit Ethernet on CAT 5+ cable)
• 802.3ae (10Gbps over fiber and co-axial)

Front 105

Electronics Industries Association & Telecommunication Industries Alliance (EIA/TIA)

Back 105

The Standards Body which creates the physical layer specifications for Ethernet

Front 106

Ethernet Cable

Back 106

A registered jack (RJ) connector with a 4 5 wiring sequence on an unshielded twisted-pair (UTP)

• Higher category cables have less attenuation and crosstalk

Front 107

Attenuation

Back 107

Loss of signal strength as data travels the length of the cable (measured in decibels (dB))

Front 108

Crosstalk

Back 108

Unwanted signal interference from adjacent pairs in the cable

Front 109

Straight Through Cable

Back 109

• A type of Ethernet cable using 4/8 wires
• The wire matches the corresponding numbers on either end
• (1-1, 2-2, 3-3, 6-6)

Front 110

Crossover Cable

Back 110

• A type of Ethernet cable using 4/8 wires
• Uses the same wires as the straight through cable but connects to different pins
• (1-3, 2-6, 3-1, 6-2)

Front 111

Rolled Cable

Back 111

• Cannot be used for any Ethernet connection
• Connects host to Console (Switch/Router)
• Each wire connects to its opposite number
• (1-8, 2-7, 3-6, 4-5)

Front 112

Cisco 3-layer Model

Back 112

• Core Layer
• Distribution Layer
• Access Layer
• (Layers are logical not physical)

Front 113

Core Layer

Back 113

• Function is to transport a large amount of data quickly
• gets data from the distribution layer and sends it back to the distribution layer after transportation

Front 114

What to Avoid at the

Core Layer

Back 114

• Anything that can slow down traffic
• Direct user connections
• Direct Server Connections
• Complex Service Policies

Front 115

The Distribution Layer

Back 115

• Provide Routing, Filtering, and WAN access to determine ho packets can access the core
• Selects the fastest way and access request can be completed
• Acts as the convergence point for all switches

Front 116

What to Keep in Mind when Designing the

Core Layer

Back 116

• Routing protocol should have low convergence time
• Network Access layer technologies should be fast with low latency
• Redundancy should be built into this layer`

Front 117

Practices generally executed at the

Distribution Layer

Back 117

• Routing between subnets and VLANS
• Implementation of security policies
• Breaking broadcast domains

Front 118

The Access Layer

Back 118

• Also known as the Desktop Layer
• The edge of the network where devices (PCs, iPads, etc) connect to the network

Front 119

Practices Generally Executed at the

Access Layer

Back 119

• Access control and policies in addition to what exists at the Distribution Layer
• Dynamic Configuration Mechanisms
• Breaking Collision Domains
• Ethernet Switching and Static Routing