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
Lans and Wans
Wans use serial connections of various types to access bandwidth.
Routers use serial connections to access the WAN
DTE: data terminal equipment (Router)
DCE: data circuit-terminating equipment (Modem)
RAM/DRAM:running config
NVRAM:startup config
Flash: OS image
ROM:Post, bootstrap
Interface: connection for packets to enter/exit the router
LAPD:used for signaling and call setup
PPP, SLIP, Frame Relay are WAN Technologies
T1, E1, xDSL, SONET are dedicated Digital Services
HDLC: High Level Data Link Control Protocol supports PPP and Multiport Configurations
Circuit Switched = POTS, ISDN =
Packet Switched = Dynamic sized cell
Cell Switched = ATM = Static sized cell
Routers use logical address to make decision
4.
CDP = Cisco Discovery Protocol = discovers neighbor routers, starts at boot,
performs router discovery
Routers can have up to 5 Telnet Connections
Ping (ICMP) operates at the Transport Layer to test Network Layer Connections
5.
ROM loads bootstrap
Flash locates and loads the OS
NVRAM locates and loads the configuration file or enters "setup" mode
(stores the startup config)
RAM (stores the running config)
If no config file is found, the system config dialog/initial configuration mode/setup
mode begins
Enable secret word is not required to be the same as enable secret password
If no config file can be found, ROM is searched
6.
7./8.
Cisco IOS Naming Conventions
Hardware Product Platform + Feature Capability + Run Location Compressed Status
NVRAM, Flash, TFTP, Rom = order configs are loaded
show version displays the boot field settings
boot system flash IOS_Filename = tells the router to boot from flash
boot system TFTP IOS_Filename IP = boot from network server
2142 = config register setting during password recovery
2102 = normal register setting
9.
TCP works at the Transport Layer
IP works at the Network Layer
Port numbers are used to keep track of the different conversations the network
at the same time
FTP = 21
TELNET = 23
SMTP = 25
DNS = 53
TFTP = 69
SNMP = 161
Exchanging initial sequence numbers during connection sequence ensures recovery
later
10.
To map domain names to IPs = identify the host names, name server, and enable
DNS
Telnet verifies the application layer software between source and destination.
most complete testing mechanism available.
Ping (ICMP) verifies the hardware connection and the logical address at the
Internet layer.
Traceroute uses TTL values to test each router along the path.
Extended ping is only in Priv Exec mode
TCP provies flow control by windowing and sequence numbers and acknolodgements.
Ports:
0-255 are for public applications
256-1024 are for marketable applications
1025-65535 are unregulated
11.
Path Determination is a layer three router function.
Routing protocols route routed protocols.
RIP (Routing Internet Protocol
, IGRP, EIGRP, OSPF
OSPF = Link State
RIP = Distance Vector
uses hop counts as metrics
hop count is greater than 15, packet is discarded.
Routing updates broadcast every 30 seconds by default
IGRP = Distance Vector
Versatility enables indefinite, complex topologies
Flexibility uses bandwidth and delay characteristics
Scalable to function in very large networks
90 Broadcast updates
Final.
IGRP must be used with an Autonomous System number
Use Show Version to display the currently running Cisco IOS version
Use Split Horizon to counteract routing loops from incorrect updates
Use Show version to display the boot field setting
If routers have a different set of LSA's, they will disagree about a link.