Module 1: WANs and Routers

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Module 1 WANs and Routers

• Semester 2
• CCNA2 Version 3.0

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Introduction to WANs

• Major characteristics of WANs
• They connect devices that are separated by wide
  geographical areas.
• They use the services of carriers such as the
  Regional Bell Operating Companies (RBOCs),
  Sprint, MCI, VPM Internet Services, Inc., and
  Altantes.net.
• They use serial connections of various types to
  access bandwidth over large geographic areas.

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Introduction to WANs cont.,

• The following devices are used in WANs
• Routers offer many services, including
  internetworking and WAN interface ports.
• Switches in the WAN provide connectivity for
  voice, data, and video communication.
• Modems include interface voice-grade services,
  channel service units/digital service units
  (CSU/DSUs) that interface T1/E1 services, and
  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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Introduction to routers in a WAN

• A router is a special type of computer. It has
  the same basic components as a standard desktop
  PC.(CPU, input/output interfaces, system bus)
• Routers connect and allow communication between
  two networks and determine the best path for data
  to travel through the connected networks.
• The main internal components of the router are
  random access memory (RAM), nonvolatile
  random-access memory (NVRAM), flash memory,
  read-only memory (ROM), and interfaces.

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Introduction to routers in a WAN

• RAM, also called dynamic RAM (DRAM), has the
  following characteristics and functions
• Stores routing tables
• Holds fast-switching cache
• Stores running configuration files
• Holds ARP cache
• Performs packet buffering (shared RAM)
• Maintains packet-hold queues
• Provides temporary memory for the configuration
  file of the router while the router is powered on
  
• Loses content when router is powered down or
  restarted

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NVRAM has the following characteristics and
functions

• Non-Volatile Random Access Memory (NVRAM)
• Provides storage for the startup configuration
  file
• Retains content when router is powered down or
  restarted

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Flash memory has the following characteristics
and functions

• Holds (stores) the operating system image (IOS)
• Allows software to be updated without removing
  and replacing chips on the processor
• Retains content when router is powered down or
  restarted
• Can store multiple versions of IOS software (in a
  2600 series router, it can be upgraded with
  single in-line memory modules)
• Is a type of electronically erasable,
  programmable ROM (EEPROM)

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Read-only memory (ROM) has the following
characteristics and functions

• Maintains instructions for power-on self test
  (POST) diagnostics
• Stores bootstrap program and basic operating
  system software
• Requires replacing pluggable chips on the
  motherboard for software upgrades

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Interfaces have the following characteristics and
functions

• Connect router to network for frame entry and
  exit
• Can be on the motherboard or on a separate module
  
• Connects the router to LANs and WANs

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Router LANs and WANs

• Routers have both LAN and WAN interfaces. In
  fact, WAN technologies are frequently used to
  connect routers and these routers communicate
  with each other by WAN connections.
• Routers are the backbone devices of large
  intranets and of the Internet. They operate at
  Layer 3 of the OSI model, making decisions based
  on network addresses.
• The two main functions of a router are the
  selection of best path for and the switching of
  frames to the proper interface.

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A correctly configured internetwork provides the
following

• Consistent end-to-end addressing
• Addresses that represent network topologies
• Best path selection (thanks to routing tables)
• Dynamic or static routing
• Switching

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Router role in a WAN

• A WAN is said to operate at the physical layer
  and at the data link layer.
• The WAN physical layer describes the interface
  between the data terminal equipment (DTE) and the
  data circuit-terminating equipment (DCE).
  Generally, the DCE is the service provider and
  the DTE is the attached device.

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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)

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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

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Academy approach to hands-on labs

• In the academy lab, devices that make up the WAN
  cloud are simulated by the connection between the
  back-to-back DTE-DCE cables. The connection
  from one router interface s0/0 to another router
  interface s0/1 simulates the whole circuit cloud.

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Router internal components

• CPU The Central Processing Unit (CPU) executes
  instructions in the operating system.
• RAM Random-access memory (RAM) is used for
  routing table information, fast switching cache,
  running configuration, and packet queues.
• Flash Flash memory is used for storage of a
  full Cisco IOS software image.
• NVRAM Nonvolatile random-access memory (NVRAM)
  is used to store the startup configuration.
• Buses Most routers contain a system bus and a
  CPU bus.
• ROM Read-only memory (ROM) is used for
  permanently storing startup diagnostic code (ROM
  Monitor).
• Interfaces The interfaces are the router
  connections to the outside. The three types of
  interfaces are local-area network (LANs),
  wide-area network (WANs), and Console/AUX.
• Power Supply The power supply provides the
  necessary power to operate the internal
  components.
• Configuration files contain instructions that a
  router uses to control the flow of traffic
  through its interfaces

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Router external connections

• The three basic types of connections on a router
  are LAN interfaces, WAN interfaces, and
  management ports.
• LAN interfaces allow the router to connect to the
  Local Area Network media. This is usually some
  form of Ethernet.
• Wide Area Network connections provide connections
  through a service provider to a distant site or
  to the Internet. These may be serial connections
  or any number of other WAN interfaces.

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Management port connections

• The console port and the auxiliary (AUX) port are
  management ports used for troubleshooting,
  monitoring and initial configuring.
• These asynchronous serial ports are not designed
  as networking ports.
• The console port is also preferred over the
  auxiliary port for troubleshooting. This is
  because it displays router startup, debugging,
  and error messages by default. The console port
  can also be used when the networking services
  have not been started or have failed. Therefore,
  the console port can be used for disaster and
  password recovery procedures.

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Connecting console interfaces

• Used for the initial configuration of the router,
  monitoring, and disaster recovery procedures.
• To connect to the console port, a rollover cable
  and a RJ-45 to DB-9 adapter are used to connect a
  PC.

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To connect the PC to a router

• 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
• Connect the RJ-45 connector of the rollover cable
  to the router console port.
• Connect the other end of the rollover cable to
  the RJ-45 to DB-9 adapter.
• Attach the female DB-9 adapter to a PC.

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Connecting LAN interfaces

• In most LAN environments, the router is connected
  to the LAN using an Ethernet or Fast Ethernet
  interface.
• A straight-through cable is used to make this
  connection. A 10/100BaseTX router interface
  requires Category 5 or better, unshielded
  twisted-pair (UTP) regardless of the router type.
  
• The correct interface must be used. If the wrong
  interface is connected, damage can result to the
  router or other networking devices. Many
  different types of connections use the same style
  of connector. For example Ethernet, ISDN BRI,
  Console, AUX, integrated CSU/DSU, and Token Ring
  interfaces use the same eight-pin connector,
  RJ-45, RJ-48, or RJ-49.

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Connecting WAN interfaces

• WAN connections may take any number of forms. A
  WAN makes data connections across a broad
  geographic area using many different types of
  technology.
• WAN services are usually leased from service
  providers. Among these WAN connection types are
  leased line, circuit-switched, and
  packet-switched.

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• For each type of WAN service, the customer
  premises equipment (CPE), often a router, is the
  data terminal equipment (DTE).
• This is connected to the service provider using a
  data circuit-terminating equipment (DCE) device,
  commonly a modem or channel service unit/data
  service unit (CSU/DSU).

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THE

• END!