cisco preparation for final exam [demo]
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DNACY CISCO GUIDE FOR FINAL EXAM
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What do we will cover in this paper:
Roles of ISP Technicians OSI model & Troubleshooting approaches Protocols Router Configuration
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Roles of ISP Technicians:When a user initially contacts the help desk to resolve an issue, the call or message is usually
directed to a Level 1 support technician. Level 1 support is usually an entry-level position that provides
junior technicians with valuable experience. Many customer issues are resolved by the Level 1 support
technician.
Issues that cannot be resolved are sent to Level 2 support, which typically has fewer agents
available. The duties and responsibilities of the Level 2 technician are similar to that of the Level 1
technician, but they are at a higher skill level. These agents are expected to solve problems that are
more challenging and require more knowledge.
First Level Support Responsibility: Diagnose basic network connectivity issues. Diagnose and document the symptoms of hardware, software and system
problems.
Resolve and document any basic user issues. Help customers complete online order forms to attain various systems,
services, hardware, software, reports and entitlements. Escalate unresolved issues to the next level.
Second Level Support Responsibility: Diagnose and solve more difficult network problems. Use diagnostic tools and remote desktop sharing tools to identify and fix
problems. Identify when an onsite technician must be dispatched to perform repairs.
Third Level Support Responsibilities: Diagnose and resolve problems that have been escalated by the level 1 and
level 2 technicians.
Survey network conditions for analysis by a senior network technician. Install and configure new equipment, including customer premise
equipment upgrades, when necessary.
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OSI MODEL
ApplicationLayer
PresentationLayer
Session Layer Transport Layer Network Layer Data Link Layer Physical Layer
Understanding OSI Model:
Application Layer:
Defines interfaces between application software and networkcommunication functions.
Provides standardized services such as file transfer between systems.Presentation Layer:
Standardizes user data formats for use between different types ofsystems. Encodes and decodes user data. Compresses and decompresses data.
Session Layer:
Manages user sessions and dialogues. Manages links between applications.
Transport Layer:
Manages end to end message delivery over the network. Can provide reliable and sequential packet delivery through error
recovery and flow control mechanisms.
Network Layer:
Provides logical network addressing. Routes packets between networks based on logical addressing.
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Data Link Layer:
Defines procedures for operating the communication links. Detects frame transmit errors and provides a recovery mechanism. Adds physical address to frame.
Physical Layer: Defines physical means of sending data over network devices. Interfaces between network medium and devices. Defines optical, electrical and mechanical characteristics for both
wired and wireless media.
Includes all form of electromagnetic transmission such as light,electricity, infrared and radio waves.
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Troubleshooting MethodologiesThere are three main troubleshooting approaches when using network models:
Top Down Bottom Up Divide and Conquer
Top Down Approach:Starts with the Application Layer and moves down. Itlooks at the problem from the point of view of the user and the application.
Bottom Up Approach:Starts with the Physical Layer and moves up. The
Physical Layer is concerned with hardware and wire connections.
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Divide and Conquer Approach:Typically troubleshooting begins at one of themiddle layers and moves up or down from there.
Troubleshooting by OSI layers:
Physical Layer:
Performance lower than baselineo Inadequate cable or poor termination can result in
errors that increase the rate of retransmissions.
o Electrical interference may cause poor performanceover copper links.
o Cabling that exceeds the recommended standarddistance limitations can cause attenuation problems.
o In a wireless networks, interference or a significantincrease in traffic can cause network responses to
degrade.
Loss of connectivityo
Intermittent loss can be caused by power relatedproblems such as failing UPS or power supply, resulting
in a device reboot or temporary link or device failure.
o Loose connections and tensions on the connectors andwires can also cause intermittent loss.
o For wireless coverage areas, intermittent connectivitycan be caused by overlapping wireless channels.
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o Complete loss can be caused by a cable connectionfailure or a failed device or interface.
High collision countso Average collision counts on shared media should
generally be below 1% of total traffico Collision based problems are often traced to a single
source, such as bad uplink cable on a hub or switch port,
or a link that is exposed to external electrical noise.
o Too many hosts on a single shared segment cancontribute to high collision rates.
o Duplex mismatches between devices can cause collisionsto be recorded on a switch link.
o A full-duplex switch port should have no collisions.
Network Diagrams:It is very difficult to troubleshoot any type of network issue,
without a network diagram that depicts the IP addresses, IP routes and
devices such as firewalls and switches. Logical and Physical topologies
are extremely useful in troubleshooting.
Physical Network Topologies:A Physical network topology shows the physical layout of the
devices connected to the network. Knowing how devices are Physically
connected is necessary for troubleshooting problems at the Physical
Layer, such as cabling or hardware problems. Physical network
topologies typically include:
Device types Models and manufacturers of devices Locations Operating System versions Cable types and identifiers Cabling endpoints
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Logical Network Topologies:A logical network topology shows how data is transferred on the
network. Symbols are used to represent network elements such as
routers, servers, hubs, hosts and security devices. Logical networktopologies typically include:
Device identifiers IP addresses and subnet masks Interface identifiers Routing protocols Static and default routes Data Link protocols WAN technologies
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ProtocolsProtocols are divided into two categories based on their use of connection:
Connection Oriented Protocols:These protocols require that a logical connection
be established between two devices before transferring data. This is generally accomplished by
following a specific set of rules that specify how a connection should be initiated, negotiated,
managed and eventually terminated. Usually one device begins by sending a request to open a
connection, and the other responds. They pass control information to determine if and how the
connection should be set up. If this is successful, data is sent between the devices. When they
are finished, the connection is lost.
Connectionless Protocols:These protocols do not establish a connection betweendevices. As soon as a device has data to send to another, it just sends it.
HTTPS: Hypertext Transfer Protocol w/ Secure Sockets Layer (SSL)Provides encrypted communication and secure identification of a network
web server. HTTPS connections are often used for payment transactions and for
sensitive data transmission.
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Router
Configuration
Changing hostname. Initial
configuration.
Router> enableRouter# configure terminalRouter(config)# hostname megatr0nz@cronusmegatr0nz@cronus(config)#
Specify an encrypted password
to prevent unauthorized access
to the router.
megatr0nz@cronus# configure terminalmegatr0nz@cronus(config)# enable secret @password@megatr0nz@cronus# end
Disable the router from
translating typos into IP
addresses.
megatr0nz@cronus# configure terminalmegatr0nz@cronus(config)# no ip domain-lookup
megatr0nz@cronus# end
Set the IP address and subnet
mask for the specified interface.
megatr0nz@cronus(config)# interface FastEthernet 0/0megatr0nz@cronus(config-if)# ip address 192.168.10.1 255.255.255.0
Set the encapsulation method
for a Serial interface.
megatr0nz@cronus# configure terminalmegatr0nz@cronus(config)# interface Serial 0/0/0megatr0nz@cronus(config-if)# encapsulation hdlc
Encrypt system passwords in
the configuration file.
megatr0nz@cronus# configure terminal
megatr0nz@cronus(config)# service password-encryption
Configure the default route. megatr0nz@cronus# configure terminalmegatr0nz@cronus(config)# ip route 0.0.0.0 0.0.0.0 Serial 0/0/0
Configure DHCP service. megatr0nz@cronus#configure terminal
megatr0nz@cronus(config)# ip dhcp pool DHCP_POOL_N1megatr0nz@cronus(dhcp-config)# network 192.168.10.0 255.255.255.0megatr0nz@cronus(dhcp-config)# dns-server 8.8.8.8megatr0nz@cronus(dhcp-config)# default-router 192.168.10.254megatr0nz@cronus(dhcp-config)# ip dhcp excluded-address 192.168.10.254
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Cisco Router Show Commands
View version information show version
View current configuration (DRAM) show running-config
View startup configuration (NVRAM) show startup-config
Show IOS file and flash space show flash
Shows all logs that the router has in its memory show log
View the interface status of an interface show interface
Overview all interfaces on the router show ip interfaces brief
View type of serial cable on Serial 0/0/0 show controllersSerial 0/0/0
Display a summary of connected cdp devices show cdp neighbor
Display detailed information on all devices show cdp entry *
Display current routing protocols show ip protocols
Display IP routing table show ip route
Display access lists, this includes the number of displayed
matches
show access-lists
Check the router can see the ISDN switch show isdn status
Check a Frame Relay PVC connections show frame-relay pvc
show lmi traffic stats show frame-relay lmi
Display the frame inverse ARP table show frame-relay map
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