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Introduction

CDP and Telnet

Enable and disable CDP Establish a Telnet connection

Verify a Telnet connection

Disconnect from a Telnet session

Suspend a Telnet session

Perform alternative connectivity tests Ping

Traceroute

Show ip route

Show interface

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Cisco Discovery Protocol Layer 2 protocol that connects network and physical layer to obtain information about

neighboring devices

When a Cisco device boots up, CDP starts up automatically and allows the device todetect neighboring devices that are also running CDP.

It runs over the data link layer and allows two systems to learn about each other, even

if they are using different network layer protocols.

Each device configured for CDP sends periodic messages, known as advertisements,to multiple routers.

Each device advertises at least one address at which it can receive Simple Network

Management Protocol (SNMP) messages.

The advertisements also contain time-to-live or holdtime information, indicating thelength of time that receiving devices should hold CDP information before discarding it.

Additionally, each device listens to periodic CDP messages sent by others in order to

learn about neighboring devices.

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CDP CDP learns:

Type of devices connected

Router interfaces they are

connected to

Model number of the devices

CDP is media and protocol independent

but runs only on Cisco devices

Router(config)#cdp run

enables CDP globally on the

router Router(config-if)#cdp enable

enables CDP on an specific

interface.

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Implementation, monitoring, andmaintenance of CDP

Router#show cdp

Router#show cdp neighbors

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Telnet Virtual terminal protocol that can be used to

verify the application layer software between

host and source.

Verify the application-layer software between

source and destination stations.

Most complete test of connectivity.

Router can have up to 5 incoming telnetsessions ( 0 to 4).

May use command telnet, connect,

hostname(if DNS or host table is available),

or IP address to connectrouter>router>connectconnectparisparis

router>router>parisparis

router>router>131.108.100.152131.108.100.152

router>router>telnettelnetparisparis

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Telnet Suspending a

Telnet session is

Press Ctrl-

Shift-6, then

x

Show sessions

displays listof current

telnet

sessions

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Telnet Telnet can be used to perform a test to determine whether or not a remote router can be

accessed.

If Telnet is used successfully to connect the York router to the Paris router, then a basic

test of the network connection is successful.

This operation can be performed at either the user or privileged EXEC levels.

If remote access can be obtained through another router, then at least one TCP/IP

application can reach the remote router.

A successful Telnet connection indicates that the upper-layer application functions

properly

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Ping Ping- uses an Echo protocol to

test connectivity, delay and if

destination is functioning. The ping user EXEC command

can be used to diagnose basicnetwork connectivity.

The command ping uses ICMP

ping ip address or hostname

! -means successfulreciept

. means timed out Udestination

unreachable

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Traceroute

The traceroute

command is the idealtool for finding where

data is being sent in a

network.

traceroute tests each

step along the way.

This operation can be

performed at either the

user or privileged

EXEC levels.

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PING/TELNET/TRACEROUTEping

uses the ICMP protocol to verify the hardwareconnection and the IP address of the network layer. This

is a basic testing mechanism.

telnet

verifies the application layer software between source

and destination. This is the most complete test

mechanism available.

traceroute allows the location of failures in the path from the source

to the destination. Trace uses Time to Live values to

generate messages from each router along the path.

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Show ip route

Show ip route

show the routing table, and how the routes were learned

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Show interfaces

Show interfaces serial

show serial connections status