Module 1: WANs and Routers

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Module 1WANs and Routers

• CCNA 2 - Version 3.0

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Introduction to WANs

• Major Characteristics of WANs
• WANs connect devices that are separated by wide
  geographical areas
• WANs use the services of carriers such as the
  Regional Bell Operating Companies (RBOCs), Sprint
  MCI
• WANs use serial connections of various types to
  access bandwidth over large geographic areas
• WANs operate at the Physical and Data-Link Layer
  of the OSI Model

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Functions of an Internetwork

• Consistent end-to-end addressing
• Best path selection (thanks to routing tables)
• Dynamic or static routing
• Switching

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WAN Devices

• Need (some of) the following to construct a WAN
• Routers - offer many services, including
  internetworking and WAN interface ports.
• Switches - provide connectivity for voice, data,
  and video communication.
• Modems - include 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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WAN Symbols
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The WAN Physical Layer

• WAN physical layer - describes the interface
  between the data terminal equipment (DTE) and the
  data circuit-terminating equipment (DCE)
• Usually
• DCE the service provider
• DTE the attached device (customer side)

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WAN Physical LayerStandards 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 LayerStandards 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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What is a Router?

• Routers
• are a special type of computer
• have some of the same basic components as a
  standard desktop PC
• CPU, input/output interfaces, system bus
• connect and allow communication between two
  networks
• determine the best path for data to travel
  through the connected networks
• Uses routing tables to best path selection

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The Role of a Router in LANs and WANs

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

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Main Internal Router Components

• random access memory (RAM)
• nonvolatile random-access memory (NVRAM)
• flash memory
• read-only memory (ROM)
• interfaces

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Main Internal Router Components
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RAM(also called Dynamic RAM or DRAM)

• Stores routing tables
• Holds fast-switching cache
• Stores running configuration (active
  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 (Non-volatile RAM)

• Stores startup configuration file (also called
  backup configuration file)
• Retains contents when router is powered down or
  restarted
• Stores a copy of routers config file

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FLASH MEMORY

• Stores Cisco image (IOS) software images
• 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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ROM (Read-Only Memory)

• 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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Router Interfaces

• Interfaces have the following characteristics and
  functions
• Connect the router to the network for frame entry
  and exit
• Can be on the motherboard or on a separate module
  
• Connects the router to LANs and WANs
• 3 types of router interfaces
• LAN interfaces (usually connect to an Ethernet
  LAN)
• WAN interfaces (provide connections through a
  service provider to a distant site or to the
  Internet)
• Console/AUX ports (asynchronous ports that
  provide for router management NOT network
  connections)

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External Router Components
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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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Management port connections

• The console port and the auxiliary (AUX) port are
  management ports used for troubleshooting,
  monitoring and initial configuring.
• Mgmt ports do NO routing
• Console port connection PC to router
• asynchronous serial ports
• non network connections

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The Console Port

• Used for
• initial configuration of the router
• monitoring
• disaster and password recovery procedures
• The console port displays router startup,
  debugging, and error messages by default
• A rollover cable, terminal emulation software and
  a RJ-45 to DB-9 adapter are needed to establish a
  terminal session between PC and router

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• The console port is also preferred over the
  auxiliary port for troubleshooting.
• Because
• displays router startup, debugging, and error
  messages by default
• No networking services to be started
• can be used for disaster and password recovery
  procedures

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Connecting a 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

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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
• 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 services are usually leased from service
  providers
• WAN connections may take any number of
  formsAmong these WAN connection types are
• leased line
• circuit-switched
• packet-switched

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• If you wanted to physically connect a router to
  all hosts on a LAN what is needed?

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Module 1WANs and Routers
THE END

• CCNA 2 - Version 3.0