Transcript Module 1

CCNA 2 v3.1 Module 1
WANs & Routers
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Wide Area Network Characteristics
• It is a data communications network
• Connect devices separated by wide
geographical area
state, province, or country
• Use the services of carrier providers
Regional Bell Operating Companies (RBOCs), Sprint,
MCI, VPM Internet Services, Inc., and Altantes.net.
• Use serial connections to access bandwidth
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How do WANs differ from LANs
• WAN data connections across a broad
geographic area
• connect company sites so that information can
be exchanged between distant offices
• Interconnect LANs
• Exchange data packets and frames between
routers and switches and the LANs they support
• What layer do WANs operate at
Datalink layer (2)
Physical layer (1)
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WAN Devices
• Routers
Connect two networks
Allow communication between two networks
Determine the best path for data to travel
• Switches provide connectivity for voice, data, and video
• Modems
Interface voice-grade services
Channel service units/digital service units (CSU/DSUs) that
interface T1/E1 services
Terminal Adapters/Network Termination 1 (TA/NT1s) that
interface Integrated Services Digital Network (ISDN) services.
• Communication servers concentrate dial-in and dial-out
user communication
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WAN DataLink layer Protocols
• Describe how frames are carried between
systems on a single data link
• Protocols designed to operate over
Dedicated point-to-point link
Multipoint link
Multi-access switched services (Frame Relay)
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WAN Standards Authroities
• International Telecommunication UnionTelecommunication Standardization Sector (ITU-T)
formerly the Consultative Committee for
International Telegraph and Telephone (CCITT)
• International Organization for Standardization (ISO)
• Internet Engineering Task Force (IETF)
• Electronic Industries Association (EIA)
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Router Components
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CPU
• The Central Processing Unit (CPU)
microprocessor
• Executes operating system instructions
System initialization
Routing functions
Network interface control
• Large routers may have multiple CPUs
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RAM
• Dynamic RAM (DRAM)
Can be upgraded using Dual In-Line Memory Modules (DIIMS
• Stores
routing tables
Running configuration – temporarily while router is on
ARP cache
Performs packet buffering – packet queues
Maintains packet-hold queues
Run time space for executable Cisco IOS software
• Volatile – power fails information is lost
• Divided into
Main processor memory
Shared input/output (I/O) memory
Shared among interfaces for temporary storage of packets
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NVRAM
• Non-Volatile Random-Access Memory
• Provides storage for the startup/backup
configuration file
• Non-volatile
Retains information when router is powered down
or restarted
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Flash Memory
• Electronically erasable, programmable ROM (EEPROM)
• Holds full copy of operating system image (IOS)
Default settings for IOS is flash
Can be in compressed or uncompressed format
Executable copy of IOS transferred to RAM during boot up
Can store multiple versions of IOS
• IOS software can updated without removing and replacing
chips on the processor
• Volatile
• To add or replace flash
Single In-Line Memory Modules (SIMMs)
PCMCIA cards can upgrade the amount of flash
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ROM
• Permanently stores startup diagnostic code
ROM Monitor
Hardware diagnositics - power-on self test (POST)
Stores bootstrap program
Loads CISCO IOS software from flash to RAM
• Not erasable
Can only be upgraded by replacing the ROM chips in the
sockets of the motherboard
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Bus
• System Bus
Used to transfer packets between the CPU and
the interfaces
• CPU Bus
Used by the CPU to transfers instructions and
data to or from specified memory addresses
Power Supply
• Provides necessary power to operate the internal
components
• Larger routers use multiple or modular power
supplies
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Interfaces
• Router connections to the outside
• Types of interfaces
LAN interfaces
Either ethernet or token ring connections
WAN interfaces
Serial, ISDN, and Integrated Channel Service Unit
(CSUs
Console / Auxilary
Serial port used for initial configuration of the router
Used for terminal sessions from coms port on
computer
• LAN and WAN configurations can be
Fixed – E1, E0, S1, S0
Modular – Fastethernet 0/0, Fastethernet 0/1, serial 0/1,
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Routers for Segmenting LAN
Routers operate at the network layer (3)
They make decisions based on IP addresses
Divide networks into smaller collision domains
Divide networks into smaller broadcast domains
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Routers have both LAN and WAN Connections
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• Making decisions based on network addresses
To determine the network address AND subnet mask
and destination ip address
• Router functions
Routers select the best path
Routers switch the frames to the proper interface
• How do routers accomplish this
Building routing tables
Exchanging network information with other routers
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• Routing tables are maintained
Statically by administrator
Dynamically by routing protocols exchanging topology
information
• A correctly configured internetwork provides
Consistent end-to-end addressing
Addresses that represent network topologies
Best path selection
Dynamic or static routing
Switching
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Routers Role in WAN
• WAN physical layer describes the interface
between DTE and DCE
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Routers
• Operate as both LAN and WAN devices
• Can exclusively be a LAN or WAN device
LAN – L1, L2, L3
WAN – L1, L2
• Can sit at the boundary between a LAN
and a WAN
LAN and WAN device at the same time
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• WAN physical layer standards and protocols:
EIA/TIA-232, EIA/TIA-449
V.24, V.35, X.21
G.703, EIA-530
ISDN, T1, T3, E1, and E3
xDSL, SONET (OC-3, OC-12, OC-48, OC-192)
• WAN data link layer standards and protocols:
High-level data link control (HDLC)
Frame Relay
Point-to-Point Protocol (PPP)
Synchronous Data Link Control (SDLC)
Serial Line Internet Protocol (SLIP)
X.25, ATM, LAPB, LAPD, LAPF
Try the interactive media lab 1.1.5
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Internal Components of 2600 Router
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External Components of 2600 Router
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LAN interfaces
Allow the router to connect to the Local Area Network media
Usually some form of Ethernet (could be Token Ring)
Wide Area Network connections
Provide connections through a service provider to a distant site
Management Connections
Console Port or Auxiliary Port
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Configuration through Console Port
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Console Port
• Used for
Initial router configuration
Monitoring
Disaster recovery procedures
(password recovery)
• Console port is preferred for troubleshooting
It displays router startup, debugging, error messages by
default
Used when networking services have not been started/
failed
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In order to configure a Router
• Terminal must support VT100 terminal emulation
HyperTerminal
• Configure terminal emulation software on the PC for:
The appropriate com port
9600 baud
8 data bits
No parity
1 stop bit
No flow control
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Modem Connection to Auxiliary Port
Used to configure router from a remote connection
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Connecting LAN Interfaces
• Ethernet Connection – E0, E1
• Fast Ethernet Connection – FastEthernet 0/0
Router communicates with LAN
Via a hub or switch
Straight Through Cable
Crossover cable used to connect router Ethernet connection
directly to a computer or another router
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WAN Connection Types
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