Basic network training2

Global Technology Services, ASEAN
IBM Confidential | 2013
Basic Network Training
Taywin Supha
Sakon Baisopon

Global Technology Services
IBM ConfidentialBasic Network Training2
 DAY2
- Transport Protocol
- Routing
• Static route
• Dynamic route
- RIP
- EIGRP
- OSPF
- Wireless LAN
Agenda

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Transport Protocol
Basic Network Training3

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Transport Protocol
 Set of rules
- for exchange control message / data
 End-to-End
 Example protocols
- User Datagram Protocol (UDP)
- Transmission Control Protocol (TCP)
Essential Switch Command Training4

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Port and Address
 IP address is the end point of identifier
- source / destination
 On same machine (same IP)
- needs identifier for each application
- multiple applications (e.g. 3 ftp sessions)
 “Port”
- 16-bit number (65,356 ports) for each IP

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Port and Address
IP address: 158.108.1.2
• Unique connection identifier
• [source IP] + [source port]
• [dest. IP] + [dest. port]
Web #1 [158.108.1.2:80]
Web #2 [158.108.1.2:8080]
Ftp [158.108.1.2:24]

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Port and Address
 Known destination IP
 Concern Issues
- destination port ?
- listen port ?
 Port numbers have the following assigned ranges:
- Numbers below 1024 are considered well-known ports numbers.
- Numbers above 1024 are dynamically assigned ports numbers.

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Well-Known Ports

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User Datagram Protocol (UDP)
 Characteristics
- No error detection/recovery
- No flow control
- No checking for existing of destination
 Simple services
 Very useful protocol

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UDP Message Format
Total length = UDP header+ Payload ≤ 216
bytes

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Protocol that use UDP
 The protocols that use UDP include:
- TFTP (Trivial File Transfer Protocol)
- SNMP (Simple Network Management Protocol)
- DHCP (Dynamic Host Control Protocol)
- DNS (Domain Name System)

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Transmission Control Protocol (TCP)
 Most popular/important in Internet
 Reliable transport protocol
 Connection-oriented
- need establishment
- [IP+source port] ↔ [IP+destination port]
- guarantee delivery / error

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TCP Message Format

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Three-Way Handshake
 TCP is a connection-oriented
protocol. TCP requires
connection establishment before
data transfer begins

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Flow Control
 Flow control avoids the problem
of a transmitting host overflowing
the buffers in the receiving host.
 TCP provides the mechanism for
flow control by allowing the
sending and receiving host to
communicate.
 The two hosts then establish a
data-transfer rate that is
agreeable to both.

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Windowing
 Windowing is a flow-control
mechanism.
 Windowing requires that the
source device receive an
acknowledgment from the
destination after transmitting a
certain amount of data.

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Windowing

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Protocol that use TCP
 The protocols that use TCP include:
- File Transfer Protocol (FTP)
- Hypertext Transfer Protocol (HTTP)
- Simple Mail Transfer Protocol (SMTP)
- Post Office Protocol (POP3)
- Telnet

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Router as a Computer
 Describe the basic purpose of a router
– Computers that specialize in sending packets over the data network
– They are responsible for interconnecting networks by selecting the best path
for a packet to travel and forwarding packets to their destination
 Routers are the network center
– Routers generally have 2 connections:
• WAN connection (Connection to ISP)
• LAN connection

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 Data is sent in form of packets between 2 end devices
 Routers are used to direct packet to its destination

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 Routers examine a packet’s destination IP address and determine the best
path by enlisting the aid of a routing table

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 Router components and their functions:
– CPU - Executes operating system instructions
– Random access memory (RAM) - Contains the running copy of configuration
file. Stores routing table. RAM contents lost when power is off.
– Read-only memory (ROM) - Holds diagnostic software used when router is
powered up. Stores the router’s bootstrap program.
– Non-volatile RAM (NVRAM) - Stores startup configuration. This may include
IP addresses (Routing protocol, Hostname of router).
– Flash memory - Contains the operating system (Cisco IOS).
– Interfaces - There exist multiple physical interfaces that are used to connect
network. Examples of interface types:
• Ethernet / fast Ethernet interfaces
• Serial interfaces
• Management interfaces

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 Router components

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 Major phases to the router boot-up process
– Test router hardware
• Power-On Self Test (POST)
• Execute bootstrap loader
– Locate & load Cisco IOS software
• Locate IOS
• Load IOS
– Locate & load startup configuration file or enter setup mode
• Bootstrap program looks for configuration file

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 Verify the router boot-up process:
– The show version command is used to view information about the router
during the bootup process. Information includes:
• Platform model number
• Image name & IOS version
• Bootstrap version stored in ROM
• Image file name & where it was loaded from
• Number & type of interfaces
• Amount of NVRAM
• Amount of flash
• Configuration register

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 Router Interface is a physical connector that enables a router to send or
receive packets
 Each interface connects to a separate network
 Consist of socket or jack found on the outside of a router
 Types of router interfaces:
– Ethernet
– Fastethernet
– Serial
– DSL
– ISDN
– Cable

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 Two major groups of Router Interfaces
– LAN Interfaces
• Are used to connect router to LAN network
• Has a layer 2 MAC address
• Can be assigned a Layer 3 IP address
• Usually consist of an RJ-45 jack
– WAN Interfaces
• Are used to connect routers to external networks that interconnect
LANs
• Depending on the WAN technology, a layer 2 address may be used
• Uses a layer 3 IP address

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 Routers and the Network Layer
– Routers use destination IP address to forward packets
• The path a packet takes is determined after a router consults information
in the routing table
• After router determines the best path
• Packet is encapsulated into a frame
• Frame is then placed on network medium in form of Bits

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 Routers Operate at Layers 1, 2 & 3
– Router receives a stream of encoded bits
– Bits are decoded and passed to layer 2
– Router de-encapsulates the frame
– Remaining packet passed up to layer 3
• Routing decision made at this layer by examining destination IP address
– Packet is then re-encapsulated & sent out outbound interface

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Configure Devices and Apply Addresses
 Implementing Basic Addressing Schemes
 When designing a new network or mapping an existing network you must
provide the following information in the form of a document:
– Topology drawing that Illustrates physical connectivity
– Address table that provides the following information:
• Device name
• Interfaces used
• IP addresses
• Default gateway

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 Basic Router Configuration
– A basic router configuration should contain the following:
• Router name - Host name should be unique.
• Banner - At a minimum, banner should warn against unauthorized
use.
• Passwords - Use strong passwords.
• Interface configurations - Specify interface type, IP address and
subnet mask. Describe purpose of interface. Issue no shutdown
command. If DCE serial interface issue clock rate command.
– After entering in the basic configuration the following tasks should be
completed:
• Verify basic configuration and router operations.
• Save the changes on a router.

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 Verify Basic Router Configuration
– Issue the show running-config command
– Save the basic router configuration by issuing the copy running-config startup-
config command
– Additional commands that will enable you to further verify router configuration
are:
• Show running-config - Displays configuration currently in RAM
• Show startup-config - Displays configuration file NVRAM
• Show IP route - Displays routing table
• Show interfaces - Displays all interface configurations
• Show IP int brief - Displays abbreviated interface configuration
information

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Routing Table Structure
 Routing Table is stored in ram and contains information about:
– Directly connected networks - this occurs when a device is connected to
another router interface
– Remotely connected networks - this is a network that is not directly connected
to a particular router
– Detailed information about the networks include source of information, network
address & subnet mask, and Ip address of next-hop router
 Show ip route command is used to view a routing table

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 Adding a connected network to the routing table
– Router interfaces
• Each router interface is a member of a different network
• Activated using the no shutdown command
• In order for static and dynamic routes to exist in routing table you must
have directly connected networks

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 Static routes in the routing table
– Includes: network address and subnet mask and IP address of next hop router
or exit interface
– Denoted with the code S in the routing table
– Routing tables must contain directly connected networks used to connect
remote networks before static or dynamic routing can be used
 When to use static routes
– When network only consists of a few routers
– Network is connected to internet only through one ISP
– Hub & spoke topology is used on a large network

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 Connected and Static routes

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 Dynamic routing protocols
– Used to add remote networks to a routing table
– Are used to discover networks
– Are used to update and maintain routing tables
 Automatic network discovery
– Routers are able discover new networks by sharing routing table information

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 Maintaining routing tables
– Dynamic routing protocols are used to share routing information with other
router & to maintain and up date their own routing table
 IP routing protocols - example of routing protocols include:
• RIP
• IGRP
• EIGRP
• OSPF

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 Routing Table Principles
– 3 principles regarding routing tables:
• Every router makes its decisions alone, based on the information it has in
its routing table
• Different routing table may contain different information
• A routing table can tell how to get to a destination but not how to get back

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 Effects of the 3 Routing Table Principles
– Packets are forwarded through the network from one router to another, on a
hop by hop basis
– Packets can take path “X” to a destination but return via path “Y” (Asymmetric
routing)

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Router Paths and Packet Switching
 Internet Protocol (IP) packet format contains fields that provide information
about the packet and the sending and receiving hosts
 Fields that are importance for CCNA students:
– Destination IP address
– Source IP address
– Version & TTL
– IP header length
– Precedence & type of service
– Packet length

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 MAC Layer Frame Format
 MAC Frames are also divided into fields - they include:
– Preamble
– Start of frame delimiter
– Destination MAC address
– Source MAC address
– Type/length
– Data and pad
– Frame check sequence

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 A Metric is a numerical value used by routing protocols help determine the
best path to a destination
– The smaller the metric value the better the path
 2 types of metrics used by routing protocols are:
– Hop count - this is the number of routers a packet must travel through to get to its
destination
– Bandwidth - this is the “speed” of a link also known as the data capacity of a link

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 Equal cost metric is a condition where a router has multiple paths to the
same destination that all have the same metric
 To solve this dilemma, a router will use Equal Cost Load Balancing - this
means the router sends packets over the multiple exit interfaces listed in
the routing table.

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 Path determination is a process used by a router to pick the best path to a
destination
 One of 3 path determinations results from searching for the best path
– Directly connected network
– Remote network
– No route determined

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 Switching Function of Router is the process used by a router to switch a
packet from an incoming interface to an outgoing interface on the same
router
– A packet received by a router will do the following:
• Strips off layer 2 headers
• Examines destination IP address located in Layer 3 header to find best
route to destination
• Re-encapsulates layer 3 packet into layer 2 frame
• Forwards frame out exit interface

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 As a packet travels from one networking device to another
– The Source and Destination IP addresses NEVER change
– The Source & Destination MAC addresses CHANGE as packet is forwarded
from one router to the next
– TTL field decrement by one until a value of zero is reached at which point
router discards packet (prevents packets from endlessly traversing the
network)

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 Path determination and switching function details. PC1 wants to send
something to PC 2.
– Step 1 - PC1 encapsulates packet into a frame - frame contains R1’s
destination MAC address

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 Step 2 - R1 receives Ethernet frame
– R1 sees that destination MAC address matches its own MAC
– R1 then strips off Ethernet frame
– R1 Examines destination IP
– R1 consults routing table looking for destination IP
– After finding destination IP in routing table, R1 now looks up next hop IP
address
– R1 re-encapsulates IP packet with a new Ethernet frame
– R1 forwards Ethernet packet out Fa0/1 interface

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 Step 3 - Packet arrives at R2
– R2 receives Ethernet frame
– R2 sees that destination MAC address matches its own MAC
– R2 then strips off Ethernet frame
– After finding destination IP in routing table, R2 now looks up next hop IP
address
– R2 re-encapsulates IP packet with a new data link frame
– R2 forwards Ethernet packet out S0/0 interface

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 Step 4 - Packet arrives at R3
– R3 receives PPP frame
– R3 then strips off PPP frame
– After finding destination IP in routing table, R3 is directly connected to destination
via its fast Ethernet interface
– R3 re-encapsulates IP packet with a new Ethernet frame
– R3 forwards Ethernet packet out Fa0/0 interface
 Step 5 - IP packet arrives at PC2 - frame is decapsulated and
processed by upper layer protocols

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General Role of the Router
 Functions of a Router
– Best Path Selections
– Forwarding packets to destination
 Introducing the Topology
– 3 1800 series routers connected via WAN links
– Each router connected to a LAN represented by a switch and a PC

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General Role of the Router
 Connections of a Router for WAN
– A router has a DB-60 port that can support 5 different cabling standards
 Connections of a Router for Ethernet
– 2 types of connectors can be used: Straight through and Cross-over
• Straight through used to connect:
– Switch-to-Router, Switch-to-PC, Router-to-Server, Hub-to-PC, Hub-
to-Server
• Cross-over used to connect:
– Switch-to-Switch, PC-to-PC, Switch-to-Hub, Hub-to-Hub, Router-to-
Router

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Routing Table and CDP Protocol
 Purpose of the debug ip routing command
– Allows you to view changes that the router performs when adding or removing
routes.
– Example:
• R2#debug ip routing
• IP routing debugging is on

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 To configure an Ethernet interface
– Example:
• R2(config)#interface fastethernet 0/0
• R2(config-if)#ip address 172.16.1.1 255.255.255.0
• R2(config-if)#no shutdown

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 When a router only has its interfaces configured & no other routing
protocols are configured then:
– The routing table contains only the directly connected networks
– Only devices on the directly connected networks are reachable

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 Checking each route in
turn
– The ping command
is used to check
end to end
connectivity

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 Purpose of CDP
– A layer 2 cisco proprietary tool used to gather information about other directly
connected Cisco devices.
 Concept of neighbors
– 2 types of neighbors:
• Layer 3 neighbors
• Layer 2 neighbors

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 CDP show commands
– Show cdp neighbors command
• Displays the following information:
– Neighbor device ID
– Local interface
– Holdtime value, in seconds
– Neighbor device capability code
– Neighbor hardware platform
– Neighbor remote port ID
– Show cdp neighbors detail command
• Useful in determining if an IP address configuration error

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 Disabling CDP
– To disable CDP globally use the following command
• Router(config)#no cdp run

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Static Routes with Exit Interfaces
 Purpose of a static route
– A manually configured route used when routing from a network to a stub
network

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 IP route command
– To configure a static route use the following command: ip route
– Example:
• Router(config)# ip route network-address subnet-mask {ip-address | exit-
interface }

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 Dissecting static route syntax
– ip route - Static route command
– 172.16.1.0 – Destination network address
– 255.255.255.0 - Subnet mask of destination network
– 172.16.2.2 - Serial 0/0/0 interface IP address on R2, which is the "next-hop" to
this network

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 Configuring routes to 2 or more remote networks
– Use the following commands for R1
• R1(config)#ip route 192.168.1.0 255.255.255.0 172.16.2.2
• R1(config)#ip route 192.168.2.0 255.255.255.0 172.16.2.2

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 Zinin’s 3 routing principles
– Principle 1: “Every router makes its decision alone, based on the information
it has in its own routing table.”
– Principle 2: “The fact that one router has certain information in its routing
table does not mean that other routers have the same information.”
– Principle 3: “Routing information about a path from one network to another
does not provide routing information about the reverse, or return path.”

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 Modifying Static routes
– Existing static routes cannot be modified. The old static route must be deleted
by placing no in front of the ip route
– Example:
• no ip route 192.168.2.0 255.255.255.0 172.16.2.2
– A new static route must be rewritten in the configuration

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 Verifying the Static Route Configuration
– Use the following commands
• Step 1 show running-config
• Step 2 verify static route has been entered correctly
• Step 3 show ip route
• Step 4 verify route was configured in routing table
• Step 5 issue ping command to verify packets can reach destination and
that Return path is working

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 Ethernet interfaces and ARP
– If a static route is configured on an Ethernet link and
packet is sent to the next-hop router then…
• The destination MAC address will be the address of the next hop’s
Ethernet interface
• This is found by the router consulting the ARP table
• If an entry isn’t found then an ARP request will be sent out

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Summary and Default Route
 Summarizing routes reduces the size of the routing table.
 Route summarization is the process of combining a number of static
routes into a single static route.

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 Configuring a summary route
– Step 1: Delete the current static route
– Step 2: Configure the summary static route
– Step 3: Verify the new static route

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 Default Static Route
– This is a route that will match all packets. Stub routers that have a number of
static routes all exiting the same interface are good candidates for a default
route.
• Like route summarization this will help reduce the size of the routing
table.
 Configuring a default static route
– Similar to configuring a static route. Except that destination IP address and
subnet mask are all zeros.
– Example:
• Router(config)#ip route 0.0.0.0 0.0.0.0 [exit-interface | ip-address ].

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 Static routes and subnet masks
– The routing table lookup process will use the most specific match when
comparing destination IP address and subnet mask
 Default static routes and subnet masks
– Since the subnet mask used on a default static route is 0.0.0.0 all packets will
match

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Static Routes and Packet Forwarding
 Packet forwarding with static routes (recall Zinin’s 3 routing principles)
 Router 1
– Packet arrives on R1’s Fastethernet 0/0 interface
– R1 does not have a route to the destination network, 192.168.2.0/24
– R1 uses the default static route

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 Packet forwarding with static routes (recall Zinin’s 3 routing principles)
 Router 2
– The packet arrives on the Serial 0/0/0 interface on R2
– R2 has a static route to 192.168.2.0/24 out Serial0/0/1

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 Packet forwarding with static routes. (recall Zinin’s 3 routing principles)
 Router 3
– The packet arrives on the Serial0/0/1 interface on R3
– R3 has a connected route to 192.168.2.0/24 out Fastethernet 0/1

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 Troubleshooting a Missing Route
 Tools that can be used to isolate routing problems include:
– Ping - tests end to end connectivity
– Traceroute - used to discover all of the hops (routers) along the path between
2 points
– Show IP route - used to display routing table & ascertain forwarding process
– Show ip interface brief - used to show status of router interfaces
– Show cdp neighbors detail - used to gather configuration information about
directly connected neighbors

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 Solving a Missing Route
 Finding a missing or mis-configured route requires methodically using the
correct tools
– Start with PING - if ping fails then use traceroute to determine where packets
are failing to arrive
 Issue: show ip route to examine routing table
– If there is a problem with a mis-configured static route remove the static route
then reconfigure the new static route

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Dynamic Routing Protocols
 Function(s) of Dynamic Routing Protocols:
– Dynamically share information between routers.
– Automatically update routing table when topology changes.
– Determine best path to a destination.

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 The purpose of a dynamic routing protocol is to:
– Discover remote networks
– Maintaining up-to-date routing information
– Choosing the best path to destination networks
– Ability to find a new best path if the current path is no longer available

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 Components of a routing protocol
– Algorithm
• In the case of a routing protocol algorithms are used for facilitating routing
information and best path determination
– Routing protocol messages
• These are messages for discovering neighbors and exchange of routing
information

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 Advantages of static routing
– It can backup multiple interfaces/networks on a router
– Easy to configure
– No extra resources are needed
– More secure
 Disadvantages of static routing
– Network changes require manual reconfiguration
– Does not scale well in large topologies

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Classifying Routing Protocols
 Dynamic routing protocols are grouped according to
characteristics. Examples include:
– RIP
– IGRP
– EIGRP
– OSPF
– IS-IS
– BGP
 Autonomous System is a group of routers under the control of a
single authority.

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 Types of routing protocols:
– Interior Gateway Protocols (IGP)
– Exterior Gateway Protocols (EGP)

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 Interior Gateway Routing Protocols (IGP)
– Used for routing inside an autonomous system & used to route within the
individual networks themselves
– Examples: RIP, EIGRP, OSPF
 Exterior Routing Protocols (EGP)
– Used for routing between autonomous systems
– Example: BGPv4

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 IGP: Comparison of Distance Vector & Link State Routing Protocols
- Distance vector
– Routes are advertised as vectors
- of distance & direction
– Incomplete view of network
- topology
– Generally, periodic
- updates
- Link state
– Complete view of network
- topology is created
– Updates are not
- periodic
-

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 Classful routing protocols
– Do NOT send subnet mask in routing
updates
 Classless routing protocols
– Do send subnet mask in routing
updates

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 Convergence is defined as when all routers’ routing tables are at a state of
consistency

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Routing Protocols Metrics
 Metric
– A value used by a routing protocol to determine which
routes are better than others

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 Metrics used in IP routing protocols
– Bandwidth
– Cost
– Delay
– Hop count
– Load
– Reliability

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 The Metric Field in the Routing
Table
 Metric used for each routing
protocol
– RIP - hop count
– IGRP & EIGRP - Bandwidth
(used by default), Delay (used
by default), Load, Reliability
– IS-IS & OSPF - Cost,
Bandwidth (Cisco’s
implementation)

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 Load balancing
– This is the ability of a router to distribute packets among
multiple same cost paths

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Administrative Distance of a Route
 Purpose of a metric
– It’s a calculated value used to determine the best path to a destination
 Purpose of Administrative Distance
– It’s a numeric value that specifies the preference of a particular route

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 Identifying the Administrative Distance (AD) in a routing table
– It is the first number in the brackets in the routing table

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 Dynamic Routing Protocols

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 Directly connected routes
– Have a default AD of 0
 Static Routes
– Administrative distance of a static route has a default value of 1

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 Directly connected routes
– Immediately appear in the routing table as soon as the interface is configured

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RIPv1
 RIP Message Format
 RIP header - divided into 3 fields
– Command field
– Version field
– Must be zero
 Route Entry - composed of 3
fields
– Address family identifier
– IP address
– Metric

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RIPv1
 RIP Operation
– RIP uses 2 message types:
• Request message
– This is sent out on startup by each RIP enabled interface
– Requests all RIP enabled neighbors to send routing table
• Response message
– Message sent to requesting router containing routing table

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RIPv1
 IP addresses initially divided into
classes
– Class A
– Class B
– Class C
 RIP is a classful routing protocol
– Does not send subnet
masks in routing
updates

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RIPv1
 Administrative Distance
– RIP’s default administrative distance is 120

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Basic RIPv1 Configuration
 A typical topology suitable for
use by RIPv1 includes:
– Three router set up
– No PCs attached to
LANs
– Use of 5 different IP
subnets

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 Router RIP Command
– To enable RIP enter:
• Router rip at the global configuration prompt
• Prompt will look like R1(config-router)#

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 Specifying Networks
– Use the network
command to:
• Enable RIP on all
interfaces that
belong to this
network
• Advertise this
network in RIP
updates sent to
other routers every
30 seconds

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Verification and Troubleshooting
 Show ip Route
 To verify and troubleshoot routing
– Use the following commands:
• show ip route
• show ip protocols
• debug ip rip

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 show ip protocols command
– Displays routing protocol configured on router

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 Debug ip rip command
– Used to display RIP routing updates as they are
happening

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 Passive interface command
– Used to prevent a router from sending updates through
an interface
– Example:
• Router(config-router)#passive-interface interface-type interface-number

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 Passive interfaces

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Similarities between RIPv1 & RIPv2
– Use of timers to prevent routing loops
– Use of split horizon or split horizon with poison
reverse
– Use of triggered updates
– Maximum hop count of 15

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EIGRP
 Roots of EIGRP: IGRP
– Developed in 1985 to overcome RIPv1’s limited hop
count
– Distance vector routing protocol
– Metrics used by IGRP
• Bandwidth (used by default)
• Delay (used by default)
• Reliability
• Load
– Discontinued support starting
with IOS 12.2(13)T & 12.2(R1s4)S

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EIGRP
 EIGRP Message Format
 EIGRP Header
– Data link frame header - contains source and destination MAC address
– IP packet header - contains source & destination IP address
– EIGRP packet header - contains AS number
– Type/Length/Field - data portion of EIGRP message

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EIGRP
 EIGRP packet header contains:
– Opcode field
– Autonomous System number
 EIGRP Parameters contain:
– Weights
– Hold time

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EIGRP
 Reliable Transport Protocol (RTP)
 Purpose of RTP
– Used by EIGRP to transmit and receive
EIGRP packets
 Characteristics of RTP
– Involves both reliable & unreliable delivery of
EIGRP packet
• Reliable delivery requires
acknowledgment from destination
• Unreliable delivery does not require
an acknowledgement from
destination
– Packets can be sent
• Unicast
• Multicast
– Using address 224.0.0.10

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EIGRP
 EIGRP’s 5 Packet Types
 Hello packets
– Used to discover & form adjacencies with neighbors

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EIGRP
 Update packets
– Used to propagate routing information

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EIGRP
 Query packets
– Used by DUAL for
searching for networks
– Can use Unicast or
Multicast
 Reply packets
– Reply packet
– Can use Unicast only
 Acknowledgement
packets
– Used to acknowledge
receipt of update, query &
reply packets

IBM Confidential
EIGRP
 Purpose of Hello Protocol
– To discover & establish adjacencies with neighbor routers
 Characteristics of hello protocol
– Time interval for sending hello packet
• Most networks it is every 5 seconds
• Multipoint non broadcast multiaccess networks
– Unicast every 60 seconds
– Holdtime
• This is the maximum time router should wait
before declaring a neighbor down
• Default holdtime
– 3 times hello interval

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EIGRP
 EIGRP Bounded Updates
– EIGRP only sends update when there is a change in route status
– Partial update
• A partial update includes only the route information that has changed –
the whole routing table is NOT sent
– Bounded update
• When a route changes, only those devices that are impacted will be
notified of the change
– EIGRP’s use of partial bounded updates minimizes use of bandwidth

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EIGRP
 Diffusing Update Algorithm (DUAL)
– Purpose
• EIGRP’s primary method for preventing routing loops
– Advantage of using DUAL
• Provides for fast convergence time by keeping a list of loop-free backup
routes

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EIGRP
 Administrative Distance (AD)
– Defined as the trustworthiness of the source route
 EIGRP default administrative distances
– Summary routes = 5
– Internal routes = 90
– Imported routes = 170

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EIGRP
 Authentication
– EIGRP can
• Encrypt routing information
• Authenticate routing information

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Basic EIGRP Configuration
 Autonomous System (AS) & Process IDs
– This is a collection of networks under the control of a single authority
(reference RFC 1930)
– AS Numbers are assigned by IANA
– Entities needing AS numbers
• ISP
• Internet Backbone prodiers
• Institutions connecting to other institutions using AS numbers

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 EIGRP autonomous system number
actually functions as a process ID
 Process ID represents an instance of
the routing protocol running on a
router
 Example
– Router(config)#router
• eigrp autonomous-system

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 The router eigrp command
 The global command that enables eigrp is
– router eigrp autonomous-system
– All routers in the EIGRP routing domain must use
the same process ID number (autonomous-system number)

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 The Network Command
 Functions of the network command
– Enables interfaces to transmit & receive EIGRP updates
– Includes network or subnet in EIGRP updates
 Example
– Router(config-router)#network network-address

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 The network Command with a Wildcard Mask
– This option is used when you want to configure
EIGRP to advertise specific subnets
– Example
• Router(config-router)#network network-address [wildcard-mask]

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 Verifying EIGRP
– EIGRP routers must establish adjacencies with their neighbors before any
updates can be sent or received
– Command used to view neighbor table and verify that EIGRP has established
adjacencies with neighbors is
• show ip eigrp neighbors

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EIGRP
 The show ip protocols
command is also used to verify
that EIGRP is enabled

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Examining the
Routing Table
– The show ip route
command is also used to
verify EIGRP
– EIGRP routes are denoted
in a routing table by the
letter “D”
– By default , EIGRP
automatically summarizes
routes at major network
boundary

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EIGRP Metric Calculation
 EIGRP Composite Metric & the K Values
– EIGRP uses the following values in its composite metric
• Bandwidth, delay, reliability, and load
– The composite metric used by EIGRP
• Formula used has values K1 K5
– K1 & K3 = 1
– all other K values = 0
-

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EIGRP Metric Calculation
 Use the sh ip protocols command to verify the K values

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Introduction to OSPF
 Background of OSPF
– Began in 1987
– 1989 OSPFv1 released in RFC 1131
– This version was experimental & never deployed
– 1991 OSPFv2 released in RFC 1247
– 1998 OSPFv2 updated in RFC 2328
– 1999 OSPFv3 published in RFC 2740

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 OSPF Packet Types

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 Hello Protocol
 OSPF Hello Packet
– Purpose of Hello
Packet
• Discover OSPF neighbors
& establish adjacencies
• Advertise guidelines on
which routers must agree
to become neighbors
• Used by multi-access
networks to elect a
designated router and a
backup designated router

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 Hello Packets continued
– Contents of a Hello Packet router ID
of transmitting router
 OSPF Hello Intervals
– Usually multicast (224.0.0.5)
– Sent every 30 seconds for NBMA
segments
 OSPF Dead Intervals
– This is the time that must transpire
before the neighbor is considered
down
– Default time is 4 times the hello
interval

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 Hello protocol packets contain information that is used in electing
– Designated Router (DR)
• DR is responsible for updating all other OSPF routers
– Backup Designated Router (BDR)
• This router takes over DR’s responsibilities if DR fails

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 OSPF Link-state Updates
– Purpose of a Link
State Update (LSU)
• Used to deliver link
state advertisements
– Purpose of a Link
State Advertisement
(LSA)
• Contains information
about neighbors &
path costs

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 OSPF Algorithm
 OSPF routers build & maintain
link-state database containing
LSA received from other routers
– Information found in database is
utilized upon execution of
Dijkstra SPF algorithm
– SPF algorithm used to create
SPF tree
– SPF tree used to populate
routing table

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 Administrative Distance
– Default Administrative Distance for OSPF is 110

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 OSPF Authentication
– Purpose is to encrypt & authenticate routing information
– This is an interface specific configuration
– Routers will only accept routing information from other
routers that have been configured with the same password
or authentication information

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Basic OSPF Configuration
 Topology used for this chapter
– Discontiguous IP addressing scheme
– Since OSPF is a classless routing protocol the subnet mask is configured in

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 The router ospf command
 To enable OSPF on a router use the following command
– R1(config)#router ospf process-id
– Process id
• A locally significant number between 1 and 65535
• This means it does not have to match other OSPF routers

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 OSPF network command
– Requires entering:
• network address
• wildcard mask - the inverse of the subnet mask
• area-id - area-id refers to the OSPF area – OSPF area is a group of
routers that share link state information
– Example: Router(config-router)#network network-address wildcard-ask area
area-id

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 Router ID
– This is an IP address used to identify a router
– 3 criteria for deriving the router ID
• Use IP address configured with OSPF router-id command
– Takes precedence over loopback and physical interface addresses
• If router-id command not used then router chooses highest IP address of
any loopback interfaces
• If no loopback interfaces are configured then the highest IP address on
any active interface is used

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 OSPF Router ID
 Commands used to verify current router ID
– Show ip protocols
– Show ip ospf
– Show ip ospf interface

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 OSPF Router ID
 Router ID & Loopback addresses
– Highest loopback address will be used as router ID if router-id command isn’t used
– Advantage of using loopback address
• The loopback interface cannot fail  OSPF stability
 The OSPF router-id command
– Introduced in IOS 12.0
– Command syntax
• Router(config)#router ospfprocess-id
• Router(config-router)#router-id ip-address
 Modifying the Router ID
– Use the command Router#clear ip ospf process

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 Verifying OSPF
 Use the show ip ospf command to verify & trouble shoot OSPF networks
 Command will display the following:
– Neighbor adjacency
• No adjacency indicated by
– Neighboring router’s Router ID is not displayed
– A state of full is not displayed
• Consequence of no adjacency
– No link state information exchanged
– Inaccurate SPF trees & routing tables

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Command Description
Show ip protocols
Displays OSPF process ID,
router ID, networks router is
advertising & administrative
distance
Show ip ospf
Displays OSPF process ID,
router ID, OSPF area
information & the last time SPF
algorithm calculated
Show ip ospf interface
Displays hello interval and dead
interval
 Verifying OSPF - Additional Commands

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 Examining the routing table
 Use the show ip route command to display the routing table
– An “O’ at the beginning of a route indicates that the router source is OSPF
– Note OSPF does not automatically summarize at major network boundaries

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OSPF Metric
 OSPF uses cost as the metric for determining the best route
– The best route will have the lowest cost
– Cost is based on bandwidth of an interface
• Cost is calculated using the formula
– 108
/ bandwidth
– Reference bandwidth
• Defaults to 100Mbps
• Can be modified using
• Auto-cost reference-bandwidth command

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OSPF Metric
 COST of an OSPF route
– Is the accumulated value from one router to the next

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 Modifying the Cost of a link
 Both sides of a serial link should be configured with the same bandwidth
– Commands used to modify bandwidth value
• Bandwidth command
– Example: Router(config-if)#bandwidthbandwidth-kbps
• ip ospf cost command – allows you to directly specify interface cost
– Example: R1(config)#interface serial 0/0/0
– R1(config-if)#ip ospf cost 1562
-

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OSPF and Multiaccess Networks
 Challenges in Multiaccess Networks
 OSPF defines five network types:
– Point-to-point
– Broadcast Multiaccess
– Nonbroadcast Multiaccess (NBMA)
– Point-to-multipoint
– Virtual links

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OSPF in Multiaccess Networks
 2 challenges presented by multiaccess networks
– Multiple adjacencies
– Extensive LSA flooding

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 Extensive flooding of LSAs
– For every LSA sent out there must be an acknowledgement of receipt sent
back to transmitting router
– Consequence: lots of bandwidth consumed and chaotic traffic

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 Solution to LSA flooding issue is the use
of
– Designated router (DR)
– Backup designated router (BDR)
 DR & BDR selection
– Routers are elected to send & receive
LSA
 Sending & Receiving LSA
– DR others send LSAs via multicast
224.0.0.6 to DR & BDR
– DR forward LSA via multicast address
224.0.0.5 to all other routers

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 DR/BDR Election Process
– DR/BDR elections DO NOT occur in point to point
networks

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 DR/BDR elections will take place on multiaccess networks as shown
below

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 Criteria for getting elected DR/BDR
1. DR: Router with the highest OSPF interface
priority
2. BDR: Router with the second highest OSPF
interface priority
3. If OSPF interface priorities are equal, the
highest router ID is used to break the tie

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 OSPF Interface Priority
 Manipulating the DR/BDR election process continued
– Use the ip ospf priority interface command.
– Example:Router(config-if)#ip ospf priority {0 - 255}
• Priority number range 0 to 255
– 0 means the router cannot become the DR or BDR
– 1 is the default priority value

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Wireless LAN

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Wireless LAN Standards
• 802.11 applies to wireless devices operating within a 1 to 2 Mbps range.
• 802.11b transmission capabilities to 11 Mbps
• 802.11a covers WLAN devices operating in the 5 GHZ transmission band
and is capable of supplying data throughput of 54 Mbps
• 802.11g provides the same throughout as 802.11a but with backwards
compatibility for 802.11b devices

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Unlicensed Frequency Bands

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Three Wireless Technologies

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Wireless Devices

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What is WLAN RF Technology?
• Data send over the air wave.
• Two-way radio communication (half duplex)
• Same radio frequency for sending and receiving.
• No licensing required for wireless products.

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2.4 GHz Channel Set

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Channel- 2.4 GHz
• 11 Channels – each channel 22 MHz wide so there are 3 non-
overlapping channels (1, 6, 11).
• 3 access points can occupy same area.

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WLAN Design Channel Reuse

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Adaptive Rate Selection

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WLAN Building Blocks
• Service Set Identifier (SSID) is the name of a wireless local area network
(WLAN). All wireless devices on a WLAN must employ the same SSID in ord
er to communicate with each other.
• Independent Basic Service Set (IBSS)

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Wireless LAN

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Roaming

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Method of WEP Authentication
• The first authentication process is the open system. This is an open
connectivity standard in which only the SSID must match.
• The second process is the shared key. This process requires the use of
Wireless Equivalency Protocol (WEP) encryption.

IBM Confidential
Wireless Security
WPA WPA2
Enterprise
mode
Authentication:
802.1x/EAP
Encryption: TKIP/MIC
Authentication: 802.1x/EAP
Encryption: AES-CCMP
Personal
mode
Authentication: PSK
Encryption: TKIP/MIC
Authentication: PSK
Encryption: AES-CCMP

IBM Confidential
Transport Protocol

IBM ConfidentialEssential Switch Command Training182

IBM Confidential
Catalyst 2960 LED Indicators
1 SYST LED 5 Speed LED
2 RPS LED 6 PoE LED1
3 Status LED 7 Mode button
4 Duplex LED 8 Port LEDs

IBM Confidential
Starting on CISCO router

IBM ConfidentialEssential Switch Command Training197

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Basic network command
Base on CISCO product

IBM Confidential
Ping Command
 This command usually used to check active connection between computer or
server.
 Ping sends out a packet to a designated network computer and measures its
response time. The target or other computer will respond and return a signal
to determine the quality of connection to other site or another computer.

IBM Confidential
Traceroute (tracert) command
 Tracert (traceroute) is another command adopted from Unix system. Actually
when you try to open facebook.com or google.com in your browser, you ask
your computer to go to that address through hopping into a few router
address.

IBM Confidential
Nslookup command
 Helps to diagnose the Domain Name System (DNS) infrastructure and comes
with a number of sub-commands.
 Resolve name to IP Address, IP Address to name, and other records on
domain name.

IBM Confidential
ipconfig command
 ipconfig used to display the TCP/IP network configuration values.
 To view switches for ipconfig use ipconfig /? command for help
- /all : show all information for all TCP/IP network
- /release : release specified adapter if you got IP address from DHCP server.
- /renew : renew and ask for new IP address from DHCP server.
- /flushdns : clear all DNS local cache
- /displaydns : displaying what do you have in your local DNS cache.

IBM Confidential
ipconfig command

IBM Confidential
Basic network troubleshooting
Base on CISCO product

IBM Confidential
Determining Route Source and Destination

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Determining L2 and L3 Address

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Introduction to Network Testing

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Testing by OSI Layer 1
• Broken cables
• Disconnected cables
• Cables connected to the wrong ports
• Intermittent cable connection
• Wrong cables used for the task at hand (must use
rollovers,
crossover cables, and straight-through cables correctly)
• Devices turned off

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• Improperly configured serial interfaces
• Improperly configured Ethernet interfaces
• Improper encapsulation set (HDLC is default for serial interfaces)
• Improper clockrate settings on serial interfaces
• Network interface card (NIC) problems

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• Routing protocol not enabled
• Wrong routing protocol enabled
• Incorrect IP addresses
• Incorrect subnet masks

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Layer 3 Troubleshooting Using Ping

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Testing Application Layer Using Telnet

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Troubleshooting Using Traceroute

Communication Cable Technologies

Cable Technology
•Data communication is accomplished with
electromagnetic energy
•A combination of electrical and magnetic
fields vibrating in relation to each other
•Includes power, voice, radio waves, infrared
light, visible light, ultraviolet light, and X,
gamma, and cosmic rays.

IBM Confidential
Q & A

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