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CCNA Flashes I.01 (Intro to Networking)

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What PC component is considered the "brains" of the computer?
The CPU is considered the "brains" of the computer. It is the PC component where most calculations take place.
What is the PC bus?
The PC bus is a collection of wires through which data is transmitted from one computer component to another. The bus connects all the PC's internal components to the CPU and RAM. Think of the bus as "highways" on which data moves from one component to another.
What is the main function of a PC motherboard?
The motherboard provides a bus and data path that connect all components to it. Everything plugs into the motherboard and depends on it to communicate with other devices. It is the nerve center of the computer system.
What is the main function of a Network Interface Card (NIC)?
The main function of a NIC is to connect a computer to a network. A computer NIC plugs into the motherboard and connects to the network through a network cable.
How many bits (b) are in a byte (B)? How many bytes (B) are in a kilobyte (KB)? How many bits (b) are in a megabyte (MB)? How many bits (b) are in a nibble?
There are 8 bits in one byte. Most computer coding schemes use 8 bits to represent each number, letter, or symbol; 1 byte represents a single addressable storage location. There are 1000 bytes in a kilobyte and 8 million bits in a megabyte. There are 4 bits in a nibble.
Convert the decimal number 167 to binary.
Convert the decimal number 167 to binary.
Convert the binary number 01100100 to decimal.
Converting a binary number to decimal is the reverse of converting a decimal number to binary. When converting from binary, look at the numbers that are considered on, and then find their place value. In the binary number 01100100, the place values 64, 32, and 4 are on. If you add together these place values, you get the decimal number 100.
Convert the binary number 0101011011000010 to hexadecimal.
Converting binary to hexadecimal is easier than it looks. No matter how large the binary number, always apply the following conversion: Break the binary number into groups of four, starting on the right and moving left. If the binary number is not divisible by 4, add 0s to the leftmost group end until there are four digits in every group. Using this conversion, 0101011011000010 is broken into the following groups: 0101 0110 1100 0010. After you have the groups, you can convert the digits to hex. 0101 is 5 in hex, 0110 is 6, 1100 is C (the 2 bits that are on are 8 and 4; adding them together produces 12, which is C in hex), and 0010 is 2. Therefore, 0101011011000010 is 0x56C2 in hex.
What are the three layers of the Cisco hierarchical model?
The three layers of the Cisco hierarchical model are: - The access layer - The distribution layer - The core layer
In the Cisco hierarchical model, what is the function of the access layer?
Sometimes referred to as the desktop layer, the access layer is the point at which users connect to the network. Some functions of the access layer include: - Connectivity into the distribution layer - Shared bandwidth - MAC address filtering (switching) - Segmentation - Provides a point at which users connect to the network - Security by allowing access lists to further optimize user needs
In the CHM which layer handles shared bandwidth.
Access layer
In the CHM which layer handles MAC address filtering (switching).
Access layer
In the CHM which layer handles segmentation.
Access layer
What is the function of the distribution layer in the Cisco hierarchical model?
Also known as the workgroup layer, the distribution layer is the demarcation point between the network's access and core layers. Its primary function is to provide boundary definition, and it's where packet manipulation takes place. Routing, route summarization, filtering, and WAN access also occur at the distribution layer. The distribution layer determines how packets access the core, so it is the layer at which policy-based connectivity is implemented. Some of the distribution layer's functions are as follows: - Collection point for access layer devices - Broadcast and multicast domain segmentation - Security and filtering services such as firewalls and access lists - Provides translation between different media types - Inter-VLAN routing - Address or area aggregation
In the CHM which layer provides boundary definition.
Distribution layer
In the CHM which layer does packet manipulation.
Distribution layer
In the CHM which layer does routing.
Distribution layer
In the CHM which layer does route summarization.
Distribution layer
In the CHM which layer does filtering.
Distribution layer
In the CHM which layer does WAN access.
Distribution layer
In the CHM which layer determines how packets access the core.
Distribution layer
At which layer of the CHM is policy-based connectivity implemented.
Distribution layer
In the CHM which layer is the collection point for access layer devices.
Distribution layer
Which layer of the CHM handles broadcast and multicast domain segmentation.
Distribution layer
At which layer of the CHM would you find firewalls.
Distribution layer
Which CHM layer provides translation between different media types.
Distribution layer
In the CHM where is inter-VLAN routing done.
Distribution layer
Where in the CHM is address or area aggregation performed.
Distribution layer
In the CHM where would one find access lists?
Access layer or distribution layer.
What is the role of the core layer in the Cisco hierarchical model?
The core layer is the backbone of the network. Its main function is to switch traffic as fast as possible. The core layer ensures that every device in the network has full reachability to all other devices. Because its function is to switch traffic as fast as possible, it should not perform any filtering to slow down traffic
What are key reasons why the OSI reference model was created? JTB
The OSI reference model was created for the following reasons: - To create standards that enable vendor interoperability by defining functional guidelines for communication between networked applications - To clarify general internetworking functions - To divide the complexity of networking into smaller, more manageable sublayers - To simplify troubleshooting - To let developers modify or improve components at one layer without having to rewrite an entire protocol stack
The ISO's OSI reference model contains seven layers. What are they? Include the layer number and the name of each layer in your answer. JTB Final
The seven layers of the OSI model are as follows: Layer 7: Application layer Layer 6: Presentation layer Layer 5: Session layer Layer 4: Transport layer Layer 3: Network layer Layer 2: Data link layer Layer 1: Physical layer
What does the application layer (Layer 7) of the OSI model do? Give some examples of this layer.
The application layer is the layer closest to the user. This means that it interacts directly with the software application. The application layer's main function is to identify and establish communication partners, determine resource availability, and synchronize communication. Some examples include the following: - TCP/IP applications such as Telnet, FTP, Simple Mail Transfer Protocol (SMTP), and HTTP - OSI applications such as Virtual Terminal Protocol; File Transfer, Access, and Management (FTAM); and Common Management Information Protocol (CMIP)
In the OSI model where would identification and establishment of communication partners take place?
Application layer (7)
In the OSI model which layer determines resource availability?
Application layer (7)
In the OSI model, which layer synchronizes communication.
Application layer (7)
In the OSI model, what are the responsibilities of the presentation layer (Layer 6)? Give some examples of this layer. 2 functions and 4 examples. JTB, Tough
Also known as the translator, the presentation layer provides coding and conversion functions to application layer data. This guarantees that the application layer on another system can read data transferred from the application layer of a different system. Some examples of the presentation layer are: - Compression and decompression - Encryption - JPEG, TIFF, GIF, PICT, QuickTime, MPEG - EBCDIC and ASCII
What OSI model layer provides coding and conversion functions to the layer above?
Presentation layer (6)
Which OSI layer guarantees that the higher layer on another system can read data transferred from the higher layer of a different system?
Presentation layer (6)
At which OSI layer are compression and decompression performed?
Presentation layer (6)
At which OSI layer is encryption performed?
Presentation layer (6)
At which OSI layer would you find JPEG?
Presentation layer (6)
At which OSI layer would you find ASCII or EBDDIC?
Presentation layer (6)
What are the functions of the session layer (Layer 5)? Give some examples. JTB
The session layer is responsible for creating, managing, and ending communication sessions between presentation layer entities. These sessions consist of service requests and responses that develop between applications located on different network devices. Some examples include SQL, RPC, X Window System, ZIP, NetBIOS names, and AppleTalk ASP.
Which OSI layer is responsible for creating communication sessions between two hosts?
Session layer (5)
Which OSI layer is responsible for managing communication sessions between two hosts?
Session layer (5)
Which OSI layer is responsible for ending communication sessions between two hosts?
Session layer (5)
What OSI layer is responsible for synchronizing dialogues between the two host's layer above and managing their data exchange?
Session layer (5)
What OSI model layer offers provisions for efficient data transfer?
Session layer (5)
What OSI model layer offers provisions for class-of-service?
Session layer (5)
What OSI model layer offers provisions for exception reporting of higher level layer problems?
Session layer (5)
At what OSI model layer would you find SQL?
Session layer (5)
At what OSI model layer would you find RPC?
Session layer (5)
At what OSI model layer would you find X-Window System?
Session layer (5)
At what OSI model layer would you find AppleTalk ZIP?
Session layer (5)
What is the transport layer (Layer 4) responsible for? Give some examples of transport layer implementations. Does 2 things, provides 7 things. JTB Final
The transport layer segments and reassembles data from upper-layer applications into data streams. It provides reliable data transmission to upper layers. End-to-end communications, flow control, multiplexing, error detection and correction, and virtual circuit management are typical transport layer functions. Some examples include TCP, UDP, and SPX. UDP does not perform error detection or correction.
What OSI layer segments data from upper-layer applications of the sending host?
Transport layer (4)
What OSI layer reassembles data into data streams on the receiving host?
Transport layer (4)
What OSI layer provides reliable data transmission to upper layers?
Transport layer (4)
What OSI layer provides end-to-end communications?
Transport layer (4)
What OSI layers provides flow control?
Transport layer (4)
What OSI layer provides multiplexing?
Transport layer (4)
Does error detection and correction occurr at the transport layer?
Yes, but not all transport protocols do so, e.g., UDP.
At what OSI layer does virtual circuit management take place?
Transport layer (4)
At what layer does UDP operate?
Transport layer (4)
At what layer does SPX operate?
Transport layer (4)
What is flow control, and what are the three methods of implementing it? 3 methods Tough
Flow control is the method of controlling the rate at which a computer sends data with the intention of preventing network congestion. The three methods of implementing flow control are: - Buffering - Source-quench messages (congestion avoidance) - Windowing
Describe the function of the network layer (Layer 3), and give some examples of network layer implementations. Provides 2 things, defines 1 thing, supports 2 protocols JTB Final
The network layer provides internetwork routing and logical network addresses. It defines how to transport traffic between devices that are not locally attached. The network layer also supports connection-oriented and connectionless services from higher-layer protocols. Routers operate at the network layer. IP, IPX, AppleTalk, and DDP are examples of network layer implementations.
At what OSI layer is support for connection-oriented services found?
Network layer (3)
At what OSI layer is support for connectionless services found?
Network layer (3)
At what OSI layer is IPX found?
Network layer (3)
At what OSI layer is AppleTalk found?
Network layer (3)
At what OSI layer is Datagram Delivery Protocol (DDP) found?
Network layer (3)
Are network layer addresses physical or logical? JTB
Network layer addresses are logical addresses specific to the network layer protocol being run on the network. Each network layer protocol has a different addressing scheme. They are usually hierarchical. They define networks first and then hosts or devices on that network. An example of a network address is an IP address, which is a 32-bit address often expressed in decimal format. 192.168.0.1 is an example of an IP address in decimal format.
What is the responsibility of the data link layer (Layer 2)?
Revised definitions from errata. The data link layer translates packets from the network layer into frames for transport onto the physical medium, and it lets the network layer control the interconnection of data circuits within the physical layer. Old definition from paper book. The data link layer provides the establishment, maintenance, and release of data-link connections among network entities and for the transfer of data-link service data units. The data link layer translates messages from the network layer into bits for transport onto the physical medium, and it lets the network layer control the interconnection of data circuits within the physical layer. Data-link specifications define different network and protocol characteristics, including physical addressing, error notification, network topology, and sequencing of frames. Data-link protocols provide delivery across individual links and are concerned with the different media types, such as 802.2 and 802.3. The data link layer is responsible for putting 1s and 0s into a logical group. These 1s and 0s are then put on the physical wire. Some examples of data link layer implementations are IEEE 802.2/802.3, IEEE 802.5/802.2, packet trailer (for Ethernet, FCS, or CRC) FDDI, HDLC, and Frame Relay.
The IEEE defines what two sublayers of the data link layer? JTB
The two sublayers of the data link layer are: - The Logical Link Control (LLC) sublayer - The MAC sublayer These two sublayers provide physical media independence.
For what is the LLC sublayer responsible? 2 responsibilities + 2 PDU types JTB Tough
The Logical Link Control (802.2) sublayer is responsible for identifying different network layer protocols and then encapsulating them to be transferred across the network. There are two types of LLC frames: service access point (SAP) and Subnetwork Access Protocol (SNAP). An LLC header conveys to the data link layer what to do with a packet after it is received.
What functions does the MAC sublayer provide? Specifies 2 things, controls 1 thing, defines 4 things JTB Tough
The MAC sublayer specifies how data is placed and transported over the physical wire. It controls access to the physical medium. The LLC layer communicates with the network layer, but the MAC layer communicates downward directly with the physical layer. Physical addressing (MAC addresses), network topologies, error notification, and delivery of frames are defined at this sublayer.
At what OSI layer is physical addressing defined?
MAC sublayer of Data Link layer (2).
At what OSI layer are network topologies defined?
MAC sublayer of Data Link layer (2).
Can error notification take place at the MAC sublayer of the Data Link layer (2)?
Yes.
At what OSI layer is delivery of frames defined?
MAC sublayer of Data Link layer (2).
What are some network devices that operate at the data link layer?
Bridges and switches are network devices that operate at the data link layer. Both devices decide what traffic to forward or drop (filter) based on MAC addresses. Logical network addresses are not used at this layer. Data link layer devices assume a flat address space.
What is the function of the OSI model's physical layer (Layer 1)? Give some examples of physical layer implementations. Defines 4 things. Includes 3 things JTB Final
The physical layer defines the physical medium. It defines the media type, the connector type, and the signaling type (baseband versus broadband). This includes voltage levels, physical data rates, and cable specifications. The physical layer is responsible for converting frames into electronic bits of data, which are then sent or received across the physical medium. Twisted pair, coaxial cable, and fiber-optic cable operate at this level. Repeaters and hubs are network devices that operate at the physical layer.
What OSI layer defines media type?
Physical (1)
What OSI layer defines connector type?
Physical (1)
What OSI layer defines signaling type (baseband versus broadband)?
Physical (1)
At what layer do repeaters operate?
Physical (1)
At what layer do hubs operate?
Physical (1)
How do the different layers of the OSI model communicate with each other? JTB
Each layer of the OSI model can communicate only with the layer above it, below it, and parallel to it (a peer layer). For example, the presentation layer can communicate with only the application layer, session layer, and presentation layer on the machine it is communicating with. These layers communicate with each other using SAPs and protocol data units (PDUs). The SAP is a conceptual location at which one OSI layer can request the services of another OSI layer. PDUs control information that is added to the user data at each layer of the model. This information resides in fields called headers (the front of the data field) and trailers (the end of the data field).
What is data encapsulation? JTB Final
A PDU can include different information as it goes up or down the OSI model. It is given a different name according to the information it is carrying (the layer it is at). When the transport layer receives upper-layer data, it adds a TCP header to the data; this is called a segment. The segment is then passed to the network layer, and an IP header is added; thus, the data becomes a packet. The packet is passed to the data link layer, thus becoming a frame. This frame is then converted into bits and is passed across the network medium. This is data encapsulation. For the CCNA test, you should know the following: - Application layer: Data - Transport layer: Segment - Network layer: Packet - Data link layer: Frame - Physical layer: Bits
At physical layer (layer 1) one finds what PDU?
Bits
At data link layer (layer 2) one finds what PDU?
Frame
At network layer (layer 3) one finds what PDU?
Packet
At transport layer (layer 4) one finds what PDU?
Segment
At application layer (layer 7) one finds what PDU?
Data

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