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CCNA Semester2
Module 4
Learning about other devices
Objectives
Cisco Discovery Protocol
Getting information about remote devices
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Discovering and Connecting to
Neighbors
Introduction to CDP
Cisco Discovery Protocol(CDP) is a Layer 2protocol that connectslower physical media andupper network layerprotocols
CDP is used to obtaininformation aboutneighboring devices
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Introduction to CDP
CDP is media and protocol independent, and
runs on all Cisco equipment over the
Subnetwork Access Protocol (SNAP). When a Cisco device boots up, CDP starts up
automatically and allows the device to detect
neighboring devices that are also running CDP.
Information obtained with CDP
CDP provides information about each CDP
neighbor device by transmitting type length
values (TLVs), which are blocks of information
embedded in CDP advertisements.
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Information obtained with CDP
Device TLVs displayed by the show cdp neighborscommand include the following: Device ID
Local Interface Holdtime
Capability
Platform
Port ID
VTP Management Domain Name (CDPv2 only)
Native VLAN (CDPv2 only)
Full/Half-Duplex (CDPv2 only)
CDP Example
Cisco
RouterD
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CDP Commands
Show cdp neighbor detail-------------------------
Device ID: SCA0425051J
Entry address(es):
IP address: 192.168.4.254
Platform: WS-C6509, Capabilities: Trans-Bridge Switch
Interface: FastEthernet0/24, Port ID (outgoing port): 3/20
Holdtime : 138 sec
Version :
WS-C6509 Software, Version McpSW: 5.4(2) NmpSW: 5.4(2)
Copyright (c) 1995-2000 by Cisco Systems
advertisement version: 2
VTP Management Domain: 'SSP'Native VLAN: 20
Duplex: full
-------------------------
Device ID: Switch
Entry address(es):
Platform: cisco WS-C2924-XL, Capabilities: Trans-Bridge Switch
Interface: FastEthernet0/23, Port ID (outgoing port): FastEthernet0/24
Holdtime : 127 sec
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Creating a network map of the environment
CDP was designed and implemented as a simple, low-
overhead protocol.
Though a CDP frame can be small, it can retrieve a great
deal of useful information about connected neighboring
Cisco devices.
Troubleshooting CDP
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Getting Information about
Remote Devices
Telnet
Telnet is a virtual terminal protocol that is partof the TCP/IP protocol suite.
It allows connections to be made to remotehosts. Telnet provides a network terminal orremote login capability.
Telnet is an IOS EXEC command used to verifythe application layersoftware between sourceand destination.
This is the most complete test mechanismavailable.
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Telnet
Telnet functions at theapplication layerof the OSImodel and depends on TCP toguarantee the correct and
orderly delivery of databetween the client and server.
A router can have multiplesimultaneous incoming Telnetsessions. The range 0 through4 is used to specify 5 VTY orTelnet lines for standard IOS.
Establishing a Telnet connection
To initiate a Telnet session any of the following
alternatives can be used:
Denver>connect paris (if DNS available)
Denver#paris
Denver>131.108.100.152
Denver>telnet paris
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Disconnecting Telnet sessions
To terminate a Telnet session any of the
following alternatives can be used:
Denver>disconnect parisDenver>exit
To suspend a Telnet session:
Press Ctrl-Shift-6, then x
To set ideal timeout (default is 10 mins):
(config-line)#exec-timeout minute [second]
Telnet process
LAB_A
LAB_B
Telnet LAB_B
Connect LAB_B
Ctrl-Shift-6 x
Enter
Resume 1
Exit
Disconnect
- Enter key will resume the most recent connection
-The resume is used with connection ID
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Ping
The ping command first sends an echo request packet to an
address, then waits for a reply. The ping is successful only if:
the echo request gets to the destination, and
the destination is able to get an echo reply back to the
source.
Ping Result
A successful echo-reply is expressed with a ! symbol
Echo-reply timeout in 2 seconds (default) is expressed with .Symbol
Change default ping settings with extended ping command
(Router)#ping [Enter]
Use Ctrl-Shift-6 escape sequence stop ping process
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Traceroute
The traceroute command isthe ideal tool for findingwhere data is being sent ina network.
The traceroute command issimilar to the pingcommand, except thatinstead of testing end-to-end connectivity, traceroutetests each step along theway.
asterisk indication meansone router is unreachable
Use Ctrl-Shift-6 escape
sequence stop tracerouteprocess
Trace Process
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Summary
Cisco Discovery Protocol-CDP
Telnet command
Ping command
Traceroute command
Lab Topology
Given access to a running network topology,
find out the following:
How devices are interconnected (physical topology)
Device name, platform
Interface name and address
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CCNA2 Module4