CCNA Notes:

Semester 1
185m = max length of a coaxial segment
single mode fiber = straight line, laser
multimode fiber = bounces in line, low power
5,4,3,2,1 rule = 5 segments, 4 repeaters, 3 with hosts, 2 link sections (without hosts), 1 collision domain 3m = max distance to connect computer to drop
6m = cross connect jumper distance (vertical distance)
90m = max distance of horizontal cable
coax = copper center
circiut switched = permanent connection network
6:
layer 2 has two sub layers - Logical Link Control \ Media Access Control
FDDI = 802.1
Ethernet = 802.3
Token Ring = 802.5
FCS = Frame Check Sequence : Check made to verify consistency of frame between host and destination
MAC operates at layer 2
MAC is a protocol that determines which computer on a shared medium is allowed to transmit
determistic = take turns (FDDI and Token Ring)
nondeterministic = first come first serve
IEEE sets standards
CRC = data within FCS that verifies data's consistency
First 6 digits of a MAC = Vendor ID
Last 6 Digits of a MAC = Unique ID
Data Rates :
Token Ring = 4 or 16 MBps/sec
FDDI = Fiber Distributed Data Interface = 100MBPs
7:
Ethernet is a proprietary term, 802.3 is not
ffffffff = broadcast
segment a LAN to isolate traffic between segments and to achieve more bandwith per user by creating smaller collision domains
switches switch in hardware /cut thru switching
bridges switch in software/store and forward (cache)
Bridges don't have IP's, pass broadcast
Routers have IP's for each interface
NICs use serial communication for the network and parallel communication for the computer
Bridges use layer 2 (MAC)
FDDI uses CSMA/CA, Dual ring topology, 4B/5B encoding
8:
cutsheet =blueprint of existing cabling
horizontal cross connect
Safety ground is connected to any exposed metal part
9:
1,2,3,6 are the most common wires used in a cable (3,6 recieve 1,2 transmit)
Telepoles are used to run cable in the ceiling
RJ-45's are used to terminate UTP cat 5
interior walls in a wiring closet should be covered with 3/4" plywood that is raised away from the underlying wall a minimum of 1 3/4"
EIA/TIA 569 = wiring closets : 1 per 1000 Sq M, 1 per 1000 Sq M thereafter
first step in locating a wiring closet = identify all nodes on the floor
crossed pair = wires in a circuit are crossed in their pins
split pair = both ends are incorrect, but cable may still work
catchment area = area with wiring bounds
62.5/125-micron multimode fiber = backbone
10.
32 bits in a subnet mask
32 bits in an IP address
11.
Routers connect two networks
ARP uses IP
RARP uses MAC
Router running proxy ARP responds with its own MAC'
RIP default update is every 30 seconds
Each router in a path is called a Hop
RIP will not go beyond 15 Hops
PDU = Protocol Data Units
Routers determine Best Path Selection
ARP tables hold info from all networks connected to them
IGRP is an IGP
Bridges and Switches use MAC to forward
Routing protocols are used to exchange routing information
static routing requires less overhead in a stub network
12. Layer 4
Ports 0-255 = Public application
255-1023 = Marketable applications
1023+ = Unregulated
3 way Handshake = Request, Acknoledge, Receive
TCP provides Flow Control and Reliability
TCP is connection oriented
UDP is connectionless
Window = number of octets that the receiver is willing to accept
Port numbers are used to track different applications that cross the network at the same time
TCP = if no ack before timeout, retransmit
Dynamic window allows for resizing during session
13. Layer 5
Session layer controls sessions between protocols
Half duplex = two way alternate communication
Full Duplex = sychonomous communication
RPC, X-windows, ASP, DNA/SCP, SQL run at the session level
Zone Information Protocol (ZIP) is Appletalk
14. Layer 6
Data Formatting, Data Encryption, and Data Compression are features of the Presentation layer
Layer 6 applies file extensions for the Application Layer
Presentation Layer Negotiates Data Layer Syntax for Application Layer
ASCII = 7bit text for servers
Epsidec = 8 bit text for mainframes
Data Compression = compacting the data into a smaller format
Data Encryption = using an algorythm to make the data secure
Data Formatting = translating between media types
15. Layer 7
Redirector = protocol that works with the OS and network clients
Telnet works at the top three layers
Domain Name = numeric address of an internet site