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CCNA Cram Sheet - FileDen

By Janice King,2014-06-17 08:12
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CCNA Cram Sheet - FileDen ...

Application

    Provides an interface between a host’s communication software and any necessary external applications

    Evaluates what resources are necessary and the available resources for communication between two devices

    Synchronises client/server applications

    Provides error control and data integrity between application

    Provides system independent processes to a host

Presentation

    Presents data to the Application layer

    Acts as a data format translator

    Handles the structuring of data and negotiating data transfer syntax to Layer 7 Processes involved include data encryption, decryption compression and decompression

Session

    Handles dialog control among devices

    Determines the beginning middle and end of a session or conversation that occurs between applications (intermediary)

Transport

    Manages end to end connections and data delivery between two hosts

    Segments and reassembles data

    Provides transparent data transfer by hiding details of the transmissions from the upper layers

Network

    Determines best path for delivery across the network

    Determines logical addressing, which can identify the destination of a packet or datagram Uses data packets (IP, IPX) and route update packets (RIP, EIGRP, and so on) Uses routed protocols IP, IPX, and AppleTalk DDP

    Devices include routers and Layer 3 switches

Data Link

    Ensures reliable data transfer from the Network layer to the Physical layer Overseas physical or hardware addressing

    Formats packets into a frame

    Provides error notification

    Devices include bridges and Layer 2 switches

Physical

    Moves bits between nodes

    Assists with the activation, maintenance, and deactivation of physical connectivity between devices Devices include hubs and repeaters

Exam Cram

    The CCNA Cram Sheet

    This Cram Sheet contains key facts about the CCNA exam. Review this information as the last thing you do before you enter the

    testing center, paying special attention to those areas in which you feel that you need the most review. You can transfer any of

    these facts from your head onto a blank sheet of paper immediately before you begin the exam.

OSI Model

    Layer Name Protocols and Devices PDU

    7 Application FTP, Telnet, TFTP, SMTP, POP3, SNMP, DNS, NTR, HTTP, HTTPS, DHCP Data

    6 Presentation ASCII, .jpg, .doc Data 5 Session RPC, SQL/Telnet (for login only) Data 4 Transport TCP Connection-oriented, reliable using PAR Segment

    UDP Connectionless, unreliable, uses upper layer protocols for reliability

    3 Network IP, ICMP, RIP, IGRP, EIGRP, OSPF Packet

    Routing and Path determination, logical addressing

    2 Data Link Ethernet, Frame Relay, PPP, HDLC Frame

    Physical (hardware) addressing (MAC addresses)

    1 Physical Bits transmitted on media Bits

    Hubs, Repeaters, Connectors

TCP and UDP Ports

    TCP Ports UDP Ports

    FTP 20, 21 DNS 53

    Telnet 23 DHCP 67, 68

    SMTP 25 TFTP 69

    DNS 53 NTP 123

    HTTP 80 SNMP 161

    POP 110

    NNTP 119

    HTTPS 443

    TCP utilises Positive Acknowledgement and Retransmission (PAR):

    ; The source device starts the timer fro each segmentl retransmits if acknowledgment is not recieved before the timer

    expires.

    ; The source device records all segments sent and expects and acknowledgment of each.

    ; The destination device acknowledges receipt of a segment by sending an ask for the next dequence number it expects.

Be able to recognise a TCP header Be able to recognise a UDP header

     Source Port Destination Port Source Port Destination Port

    Sequence Number Length Checksum

    Acknowledgment Number

    Misc. Flags Window Size

    Checksum Urgent

    Options

    CDP

    ; Proprietary (Cisco only) Data Link (Layer 2) protocol

    ; L3 protocol and media independent

    ; Uses L2 multicast to gather hardware and protocol information about directly connected devices.

    ; Enabled by default; can be disabled globally by no cdp run.

    ; To learn remote device L3 addresses, hardware platform and IOS ver, use

    Show cdp neighbor detail

    or

    show cdp entry *

Lan Technology

    ; Ethernet physical addressing = MAC addresses.

    o 12 hexadecimal digits

    o First six digits are OUI of NIC manufacturer

    ; PC to switch/hub = straight-through cable

    ; Hub-hub, switch-switch, PC-PC, router-router, PC-router directly (no switch/hub): use cross-over cable

    ; Switches, bridges, and routers segment a network. Hubs and repeaters EXTEND a network.

; Switches increase the number of collision domains, do not segment broadcase domains. Routers, L3 switches, and VLANs

    segment broadcast domains.

Switching

    ; A switch is a multiport bridge. Switches forward frames using hardware ASIC, making them faster than bridges. Dedicated

    bandwidth per port.

    ; Bridges and switches learn MACs by reading the source MAC of each frame. ; Switches operate in one of three modes:

    o Store-and-ForwardL Entire frame is buffered. FCS is run (error checking).

    o Cut-throughL Only destination MAC is read, frame is forwarded.

    o Fragment-Free: First 64 bytes of frame are buffered, frame is forwarded,. Cisco proprietary. ; Half-duplex: Shared collision domain and lower throughtput

    ; Full-duplex: Point-to-point and higher throughput

    ; To remotely manage a switch, you need an IP address, subnet mask, and default gateway. The switch must be reachable on

    a port in its maangement VLAN.

VLANs:

    ; Logically divide a switch into multiple, independent switches at L2 ; Create separate broadcast domains in a switch, increasing the number of broadcast domains ; Span multiple switches using trunks

    ; Allow logical grouping of users by function

    ; Simplify adding, moving, and changing hosts in the network

    ; Enhance security

    VLAN configuration steps:

    1. The VLAN must be created.

    2. The VLAN may be named.

    3. The desired ports must be added to the new VLAN.

    4. Routing between VLANs requires a router or a Layer 3 switch.

Trunks

    Trunks carry traffic from multiple VLANs over a single connection (cross-over cable). The VLAN ID is tagged using one of two

    methods:

    1. ISL

    2. IEEE 802.1q

    ; A trunk can operate in one of five modes:

    o Dynamic Auto

    o Dynamic Desirable

    o On

    o Off

    o Nonegotiate

VTP (VLAN Trunking Protocol)

    VTP simplifies VLAN administration. Configuration of VLANs is distributed to all switches in a VTP domain from a single server-mode

    swtich.

    The three VTP modes are as follows:

    ; Server

    ; Client

    ; Transparent

    ; Switches must be in the same VTP domain, and must use the same password to exchange VTP information.