WANs and Router Basics

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WANs and Router Basics

• Semester 2
• Chapter 2 WANs Routers

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Table of Contents

• WAN Devices
• WAN Standards
• WAN Technologies
• Router Basics
• Router User Interface

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WAN Devices

• WAN Routers
• WAN Switches
• WAN Servers
• Modems and other connection devices

Table of Contents
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WAN Services

• WANs provide for the exchange of data
  packets/frames between the LANs they support.
• A WAN interconnects LANs that are usually
  separated by large geographic areas.
• WANs often move traffic at lower than LAN speeds.
• WAN devices include

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Routers

• Routers maintain their role as traffic cops
• Routers can operate as...
• Internal Routers
• Backbone Routers
• Area Border Routers
• Autonomous System Boundary Routers

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WAN Switches

• Service provider equipment that connects to WAN
  bandwidth for voice, data and video
  communications. They function much like a LAN
  switch but carrying larger amounts of traffic and
  usually a specific WAN technology.

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Modems and other connection devices

• Sometimes just special ports on a router, special
  configurations on a router, sometime separate
  devices like modems.
• Interface the existing LAN technology with the
  WAN technology they are connected to. These
  devices are specific to each technology.

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WAN Servers

• Concentrates dial-in and dial-out services.
• Equipment is usually at the service providers
  site.

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WAN Standards
Table of Contents
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WAN Standards

• What layers of the OSI model do WAN standards
  describe?
• Physical and Data Link Layers

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WAN Physical Layer

• Protocols that describe how to provide
  electrical, mechanical, operational, and
  functional connections for WAN services.
• These services are most often obtained from WAN
  service providers such as telephone companies,
  cable companies, and dedicated fiber sellers.

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WAN Physical Layer

• Several physical layer standards specifying this
  interface between the ISP and your router are...
• EIA/TIA-232
• EIA/TIA-449
• V.24
• V.35
• X.21
• G.703
• EIA-530

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WAN Data-Link Layer

• WAN data link protocols describe how frames are
  carried between systems on a single data link.
• They include protocols designed to operate over
  all physical layer standards.
• Most common Layer 2 WAN Technologies include

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WAN Data-Link Encapsulations

• High-Level Data Link Control (HDLC)
• Cisco default encapsulation typically used
  between routers running Cisco IOS
• Streamlined not a lot of overhead
• Frame Relay
• uses high-quality digital facilities
• uses simplified framing with no error correction
  mechanisms (connectionless!!)
• New Becoming more and more popular

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WAN Data-Link Encapsulations

• PPP (Point-to-Point Protocol)
• A little slower
• Can check for link quality and allows password
  authentication at Layer 2
• Not proprietary so used more often than HDLC for
  less expensive WAN connections.

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WAN Technologies

• The following overview of WAN categories uses
  some of the physical and data link layer
  standards we talked about.

Table of Contents
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WAN Technologies Overview

• Dedicated
• T1, E1, T3, E3
• xDSL
• SONET

• Analog
• Dial-up modems
• Cable modems
• Wireless

Switched

• Packet Switched
• X.25
• Frame
• Relay

• Circuit Switched
• POTS
• ISDN

• Cell Switched
• ATM
• SMDS

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WAN Technologies Overview

• Dedicated
• T1, E1, T3, E3
• xDSL
• SONET

• Analog
• Dial-up modems
• Cable modems
• Wireless

Switched

• Packet Switched
• X.25
• Frame
• Relay

• Circuit Switched
• POTS
• ISDN

• Cell Switched
• ATM
• SMDS

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Dedicated Digital Services
Dedicated Digital Services provide full-time
connectivity through a point-to-point link

• T series in U.S. and E series in Europe
• Uses time division multiplexing to slice up
  data and assign time slots for transmissions
• T1 1.544 Mbps
• T3 44.736 Mbps
• E1 2.048 Mbps
• E3 34.368 Mbps

• Uses twisted pair fiber
• Extremely popular
• Moderate cost

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Dedicated Digital Services

• Digital Subscriber Lines (xDSL) the x stands for
  a family of technologies
• New WAN Technology for home use decreasing
  bandwidth with increasing distance from the phone
  companies CO.
• Data rates as high as 51.84 Mbps but more common
  to be in the 100s of Kbps
• Varieties include HDSL, SDSL, ADSL, VDSL
• Moderate expense and getting cheaper

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Dedicated Digital Services

• Synchronous Optical Network (SONET)
• Specialized high bandwidth technology for use at
  various Optical Carrier speeds (OC) ranging from
  51.84 Mbps (OC-1) to 9,952 Mbps (OC-192)
• Uses lasers to divide the wavelength of the light
  into sections that can carry large amounts of
  data (Wave Division Multiplexing)
• Very expensive used by large ISPs and other
  Internet backbone entities.

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WAN Technologies Overview

• Dedicated
• T1, E1, T3, E3
• xDSL
• SONET

• Analog
• Dial-up modems
• Cable modems
• Wireless

Switched

• Packet Switched
• X.25
• Frame
• Relay

• Circuit Switched
• POTS
• ISDN

• Cell Switched
• ATM
• SMDS

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Analog Services

• Dial-up Modems (switched analog)
• Limited to 56 kbps
• Works with existing phone network
• Low cost and widespread usage

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Analog Services

• Cable Modems (Shared Analog)
• Puts data signals on the same cable as television
  signals
• Increasing in popularity
• Maximum bandwidth can be 10 Mbps, though this
  degrades as more users attach to a given network
  segment (behaving like an unswitched LAN)
• Cost is relatively low usage is small but
  increasing the medium is coaxial cable.

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Analog Services
Wireless

• Terrestrial
• Bandwidths typically in the 11 Mbps range
• Cost is relatively low
• Line-of-sight is usually required
• Usage is moderate

• Satellite
• Can serve mobile users and remote users
• Usage is widespread
• Cost is very high

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WAN Technologies Overview

• Dedicated
• T1, E1, T3, E3
• xDSL
• SONET

• Analog
• Dial-up modems
• Cable modems
• Wireless

Switched

• Packet Switched
• X.25
• Frame
• Relay

• Circuit Switched
• POTS
• ISDN

• Cell Switched
• ATM
• SMDS

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Circuit Switched Services

• Plain Old Telephone System (POTS)
• Not a computer data service but...
• POTS is an important component of our
  communication infrastructure and
• It is still the standard for designing reliable
  networks

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Circuit Switched Services

• Integrated Services Digital Network (ISDN)
• Historically important--first dial-up digital
  service
• Cost is moderate max. bandwidth 128 kbps for
  BRI (Basic Rate Interface)
• 2 B channels _at_ 64kps and 1 D channel _at_ 16kps
• B channels are voice/data channels D for
  signaling

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WAN Technologies Overview

• Dedicated
• T1, E1, T3, E3
• xDSL
• SONET

• Analog
• Dial-up modems
• Cable modems
• Wireless

Switched

• Packet Switched
• X.25
• Frame
• Relay

• Circuit Switched
• POTS
• ISDN

• Cell Switched
• ATM
• SMDS

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Packet Switched Services

• X.25 (Connection-oriented)
• Older WAN technology developed in 1970s
• Reliable--X.25 has been extensively debugged and
  is now very stable--literally no errors in modern
  X.25 networks
• Store Forward--Since X.25 stores the whole
  frame to error check it before forwarding it on
  to the destination, it has an inherent delay
  (unlike Frame Relay) and requires large,
  expensive memory buffering capabilities.

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Packet Switched Services

• Frame Relay (Connectionless)
• More efficient and much faster than X.25
• Packet switched version of ISDN (which is circuit
  switched) data rates up to 44.736Mbps with
  56kbps and 384kbps being the most popular
• Used mostly to forward LAN IP and IPX packets but
  can be used to forward other types of traffic
• Primary competitive advantage is its low cost

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WAN Technologies Overview

• Dedicated
• T1, E1, T3, E3
• xDSL
• SONET

• Analog
• Dial-up modems
• Cable modems
• Wireless

Switched

• Packet Switched
• X.25
• Frame
• Relay

• Circuit Switched
• POTS
• ISDN

• Cell Switched
• ATM
• SMDS

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Cell Switched Services

• Asynchronous Transfer Mode (ATM)
• Relatively new WAN Technology related to
  broadband ISDN max. bandwidth 622 Mbps
• Developed in order to provide one technology for
  both WANs and LANs to transport data, video, and
  voice. (High Cost)
• Key Benefits
• One network for all traffic--voice, data, video
• Compatible with current wiring infrastructure
  (cable plant)
• Very flexible and scalable
• Simplifies network management

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Cell Switched Services

• Switched Multimegabit Data Service (SMDS)
• Closely related to ATM SMDS is the MAN
  (Metropolitan Area Network) implementation of ATM
• High Cost with max. bandwidth 44.736 Mbps

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Router Basics
Table of Contents
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Internal Components
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RAM

• Temporary storage for router configuration files
• RAM content is lost on power down or restart
• Stores...
• Routing tables
• ARP cache
• Fast switching cache
• Packet buffering
• And Packet hold queues

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NVRAM

• Non-volatile RAM
• Stores backup/startup configuration files
• Content is not lost when router is powered down
  or restarted.

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Flash

• Holds the Cisco IOS (Internet Operating System)
• Allows updating of software without replacing the
  Flash chip
• Multiple versions of IOS can be stored
• Retained on power down

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ROM

• Contains POST (Power On Self Test)
• A bootstrap program (loads the Cisco IOS)
• And operating system software
• Backup, trimmed down version of the IOS
• Upgrades require installing new chip set

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Interfaces

• Network connections through which packets enter
  and exit the router
• Attached to the motherboard or as separate
  modules.

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Router User Interface
Table of Contents
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User EXEC Modes

• User mode
• Limited mode used for checking the routers
  status, looking at routing tables, etc.
• You cannot configure the router
• Once youve typed the password to enter user
  mode, you will see the gt prompt. The word
  Router will be the name of the router.
• Password
• Routergt

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Privileged EXEC Modes

• Privileged mode
• Does everything User mode does
• Full power to configure the router
• In user mode, you enter the command enable and
  then the privileged password
• Routergt enable
• Password
• Router

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Command Lists

• To get a list of commands available in either
  user mode or privileged mode, enter a ? at the
  prompt.
• Routergt ?
• Router ?
• Since the available commands will be more than
  the screen can hold, you will get the --More--
  message at the bottom.
• Hitting the space bar will advance the screen to
  show the next page.

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Getting Help on a Command

• The ? can be used with a partial command to learn
  all the available commands that match what you
  entered.
• To use this help feature, enter the partial
  command, then tap the space bar, then type ?
• For example...

ip flash interfaces ipx version parser
Router show ?
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Error Indicator

• When youve entered an error in the command
  string, a carat () symbol will indicate where
  the error occurred.
• For example...

Router show runing-config
Invalid input detected at the marker
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Labs

• We are going to do 2 basic router labs so you can
  get a feel for their hardware and software
  components. If you go on to the Cisco Networking
  Academy, you will work with them extensively.