Itep

661 Ping 127001- Testing the Local stack

Ping is a utility for testing IP connectivity between hosts Ping sends out requests for responses from a specified host address Ping uses a Layer 3 protocol that is a part on the TCPIP suite called Internet Control Message Protocol (ICMP) Ping uses an ICMP Echo Request datagram

If the host at the specified address receives the Echo request it responds with an ICMP Echo Reply datagram For each packet sent ping measures the time required for the reply

As each response is received ping provides a display of the time between the ping being sent and the response received This is a measure of the network performance Ping has a timeout value for the response If a response is not received within that timeout ping gives up and provides a message indicating that a response was not received

After all the requests are sent the ping utility provides an output with the summary of the responses This output includes the success rate and average round-trip time to the destination

Pinging the Local Loopback

There are some special testing and verification cases for which we can use ping One case is for testing the internal configuration of IP on the local host To perform this test we ping the special reserve address of local loopback (127001) as shown in the figure

A response from 127001 indicates that IP is properly installed on the host This response comes from the Network layer This response is not however an indication that the addresses masks or gateways are properly configured Nor does it indicate anything about the status of the lower layer of the network stack This simply tests IP down through the Network layer of the IP protocol If we get an error message it is an indication that TCPIP is not operational on the host

671 Lab- Ping and Traceroute

This lab demonstrates the ping and tracert commands from a host You will observe the steps of the operation of these commands in a network

Lab 671 Ping and TracerouteTopology Diagram

Addressing Table

Device Interface IP Address Subnet Mask Default Gateway

Learning ObjectivesUpon completion of this lab you will be able tobull Use the ping command to verify simple TCPIP network connectivitybull Use the tracerttraceroute command to verify TCPIP connectivityBackgroundTwo tools that are indispensable when testing TCPIP network connectivity are ping and tracert Theping utility is available on Windows Linux and Cisco IOS and tests network connectivity The tracertutility is available on Windows and a similar utility traceroute is available on Linux and Cisco IOS Inaddition to testing for connectivity tracert can be used to check for network latencyFor example when a web browser fails to connect to a web server the problem can be anywherebetween client and the server A network engineer may use the ping command to test for local networkconnectivity or connections where there are few devices In a complex network the tracert commandwould be used Where to begin connectivity tests has been the subject of much debate it usuallydepends on the experience of the network engineer and familiarity with the networkThe Internet Control Message Protocol (ICMP) is used by both ping and tracert to send messagesbetween devices ICMP is a TCPIP Network layer protocol first defined in RFC 792 September 1981ICMP message types were later expanded in RFC 1700ScenarioIn this lab the ping and tracert commands will be examined and command options will be used to

modify the command behavior To familiarize the students with the use of the commands devices in theCisco lab will be testedMeasured delay time will probably be less than those on a production network This is because there islittle network traffic in the Eagle 1 labTask 1 Use the ping Command to Verify Simple TCPIP Network ConnectivityThe ping command is used to verify TCPIP Network layer connectivity on the local host computer oranother device in the network The command can be used with a destination IP address or qualifiedname such as eagle-serverexamplecom to test domain name services (DNS) functionality For this labonly IP addresses will be usedThe ping operation is straightforward The source computer sends an ICMP echo request to thedestination The destination responds with an echo reply If there is a break between the source anddestination a router may respond with an ICMP message that the host is unknown or the destinationnetwork is unknownStep 1 Verify TCPIP Network layer connectivity on the local host computerCgt ipconfigWindows IP ConfigurationEthernet adapter Local Area ConnectionConnection-specific DNS Suffix IP Address 1721612Subnet Mask 25525500Default Gateway 17216255254CgtFigure 1 Local TCPIP Network InformationCCNA

Learning ObjectivesUpon completion of this lab you will be able tobull Use the ping command to verify simple TCPIP network connectivitybull Use the tracerttraceroute command to verify TCPIP connectivityBackgroundTwo tools that are indispensable when testing TCPIP network connectivity are ping and tracert Theping utility is available on Windows Linux and Cisco IOS and tests network connectivity The tracertutility is available on Windows and a similar utility traceroute is available on Linux and Cisco IOS Inaddition to testing for connectivity tracert can be used to check for network latencyFor example when a web browser fails to connect to a web server the problem can be anywherebetween client and the server A network engineer may use the ping command to test for local networkconnectivity or connections where there are few devices In a complex network the tracert command

would be used Where to begin connectivity tests has been the subject of much debate it usuallydepends on the experience of the network engineer and familiarity with the networkThe Internet Control Message Protocol (ICMP) is used by both ping and tracert to send messagesbetween devices ICMP is a TCPIP Network layer protocol first defined in RFC 792 September 1981ICMP message types were later expanded in RFC 1700ScenarioIn this lab the ping and tracert commands will be examined and command options will be used tomodify the command behavior To familiarize the students with the use of the commands devices in theCisco lab will be testedMeasured delay time will probably be less than those on a production network This is because there islittle network traffic in the Eagle 1 labTask 1 Use the ping Command to Verify Simple TCPIP Network ConnectivityThe ping command is used to verify TCPIP Network layer connectivity on the local host computer oranother device in the network The command can be used with a destination IP address or qualifiedname such as eagle-serverexamplecom to test domain name services (DNS) functionality For this labonly IP addresses will be usedThe ping operation is straightforward The source computer sends an ICMP echo request to thedestination The destination responds with an echo reply If there is a break between the source anddestination a router may respond with an ICMP message that the host is unknown or the destinationnetwork is unknownStep 1 Verify TCPIP Network layer connectivity on the local host computerCgt ipconfigWindows IP ConfigurationEthernet adapter Local Area ConnectionConnection-specific DNS Suffix IP Address 1721612Subnet Mask 25525500Default Gateway 17216255254CgtFigure 1 Local TCPIP Network InformationCCNA ExplorationNetwork Fundamentals Addressing the Network - IPV4 Lab 671 Ping and TracerouteAll contents are Copyright copy 1992ndash2007 Cisco Systems Inc All rights reserved This document is Cisco Public Information Page 3 of 8

1 Open a Windows terminal and determine IP address of the pod host computer with theipconfig command as shown in Figure 1The output should look the same except for the IP address Each pod host computer should havethe same network mask and default gateway address only the IP address may differ If theinformation is missing or if the subnet mask and default gateway are different reconfigure the

TCPIP settings to match the settings for this pod host computer2 Record information about local TCPIP network informationTCPIP Information ValueIP AddressSubnet MaskDefault GatewayFigure 2 Output of the ping Command on the Local TCPIP Stack3 Use the ping command to verify TCPIP Network layer connectivity on the local host computerBy default four ping requests are sent to the destination and reply information is received Outputshould look similar to that shown in Figure 21048686 Destination address set to the IP address for the local computer1048686 Reply informationbytesmdashsize of the ICMP packettimemdashelapsed time between transmission and replyTTLmdashdefault TTL value of the DESTINATION device minus the number of routers in thepath The maximum TTL value is 255 and for newer Windows machines the defaultvalue is 1281048686 Summary information about the replies1048686 Packets Sentmdashnumber of packets transmitted By default four packets are sent1048686 Packets Receivedmdashnumber of packets received1048686 Packets Lost mdashdifference between number of packets sent and received1048686 Information about the delay in replies measured in milliseconds Lower round triptimes indicate faster links A computer timer is set to 10 milliseconds Values faster than10 milliseconds will display 0CCNA

4 Fill in the results of the ping command on your computerField ValueSize of packetNumber of packets sentNumber of repliesNumber of lost packetsMinimum delayMaximum delayAverage delayStep 2 Verify TCPIP Network layer connectivity on the LANCgt ping 17216255254Pinging 17216255254 with 32 bytes of dataReply from 17216255254 bytes=32 time=1ms TTL=255Reply from 17216255254 bytes=32 timelt1ms TTL=255Reply from 17216255254 bytes=32 timelt1ms TTL=255Reply from 17216255254 bytes=32 timelt1ms TTL=255Ping statistics for 17216255254Packets Sent = 4 Received = 4 Lost = 0 (0 loss)Approximate round trip times in milli-secondsMinimum = 0ms Maximum = 1ms Average = 0msCgtFigure 3 Output of the ping Command to the Default Gateway

1 Use the ping command to verify TCPIP Network layer connectivity to the default gatewayResults should be similar to those shown in Figure 3Cisco IOS default TTL value is set to 255 Because the datagrams did not travel through a routerthe TTL value returned is 2552 Fill in the results of the ping command to the default GatewayField ValueSize of packetNumber of packets sentNumber of repliesNumber of lost packetsMinimum delayMaximum delayAverage delayWhat would be the result of a loss of connectivity to the default gateway___________________________________________________________________________________CCNA ExplorationNetwork Fundamentals Addressing the Network - IPV4 Lab 671 Ping and TracerouteAll contents are Copyright copy 1992ndash2007 Cisco Systems Inc All rights reserved This document is Cisco Public Information Page 5 of 8

Step 3 Verify TCPIP Network layer connectivity to a remote networkCgt ping 192168254254Pinging 192168254254 with 32 bytes of dataReply from 192168254254 bytes=32 timelt1ms TTL=62Reply from 192168254254 bytes=32 timelt1ms TTL=62Reply from 192168254254 bytes=32 timelt1ms TTL=62Reply from 192168254254 bytes=32 timelt1ms TTL=62Ping statistics for 192168254254Packets Sent = 4 Received = 4 Lost = 0 (0 loss)Approximate round trip times in milli-secondsMinimum = 0ms Maximum = 0ms Average = 0msCgtFigure 4 Output of the ping Command to Eagle Server1 Use the ping command to verify TCPIP Network layer connectivity to a device on a remotenetwork In this case Eagle Server will be used Results should be similar to those shown inFigure 4Linux default TTL value is set to 64 Since the datagrams traveled through two routers to reachEagle Server the returned TTL value is 622 Fill in the results of the ping command on your computerField ValueSize of packetNumber of packets sentNumber of repliesNumber of lost packetsMinimum delayMaximum delayAverage delayC gt ping 192168254254Pinging 192168254254 with 32 bytes of dataRequest timed outRequest timed outRequest timed out

Request timed outPing statistics for 192168254254Packets Sent = 4 Received = 0 Lost = 4 (100 loss)CgtFigure 5 Output of a ping Command with Lost PacketsThe ping command is extremely useful when troubleshooting network connectivity However there arelimitations In Figure 5 the output shows that a user cannot reach Eagle Server Is the problem withEagle Server or a device in the path The tracert command examined next can display networklatency and path informationCCNA

Task 2 Use the tracert Command to Verify TCPIP ConnectivityThe tracert command is useful for learning about network latency and path information Instead ofusing the ping command to test connectivity of each device to the destination one by one the tracertcommand can be usedOn Linux and Cisco IOS devices the equivalent command is tracerouteStep 1 Verify TCPIP Network layer connectivity with the tracert command1 Open a Windows terminal and issue the following commandCgt tracert 192168254254Cgt tracert 192168254254Tracing route to 192168254254 over a maximum of 30 hops1 lt1 ms lt1 ms lt1 ms 172162552542 lt1 ms lt1 ms lt1 ms 10101063 lt1 ms lt1 ms lt1 ms 192168254254Trace completeCgtFigure 6 Output of the tracrt command to Eagle ServerOutput from the tracert command should be similar to that shown in Figure 62 Record your result in the following tableField ValueMaximum number of hopsFirst router IP addressSecond router IP addressDestination reachedStep 2 Observe tracert output to a host that lost network connectivityIf there is a loss of connectivity to an end device such as Eagle Server the tracert command can givevaluable clues as to the source of the problem The ping command would show the failure but not anyother kind of information about the devices in the path Referring to the Eagle 1 lab Topology Diagramboth R2-Central and R1-ISP are used for connectivity between the pod host computers and Eagle ServerCgt tracert -w 5 -h 4 192168254254Tracing route to 192168254254 over a maximum of 4 hops1 lt1 ms lt1 ms lt1 ms 172162552542 lt1 ms lt1 ms lt1 ms 10101063 Request timed out4 Request timed outTrace complete

CgtFigure 7 Output of the tracert CommandRefer to Figure 7 Options are used with the tracert command to reduce wait time (in milliseconds) -w5 and maximum hop count -h 4 If Eagle Server was disconnected from the network the defaultgateway would respond correctly as well as R1-ISP The problem must be on the 192168254024network In this example Eagle Server has been turned offCCNA ExplorationNetwork Fundamentals Addressing the Network - IPV4 Lab 671 Ping and TracerouteAll contents are Copyright copy 1992ndash2007 Cisco Systems Inc All rights reserved This document is Cisco Public Information Page 7 of 8

What would the tracert output be if R1-ISP failed___________________________________________________________________________________What would the tracert output be if R2-Central failed___________________________________________________________________________________Task 3 ChallengeThe default values for the ping command normally work for most troubleshooting scenarios There aretimes however when fine tuning ping options may be useful Issuing the ping command without anydestination address will display the options shown in Figure 8Cgt pingUsage ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS][-r count] [-s count] [[-j host-list] | [-k host-list]][-w timeout] target_nameOptions-t Ping the specified host until stoppedTo see statistics and continue - type Control-BreakTo stop - type Control-C-a Resolve addresses to hostnames-n count Number of echo requests to send-l size Send buffer size-f Set Dont Fragment flag in packet-i TTL Time To Live-v TOS Type Of Service-r count Record route for count hops-s count Timestamp for count hops-j host-list Loose source route along host-list-k host-list Strict source route along host-list-w timeout Timeout in milliseconds to wait for each replyCgtFigure 8 Output of a ping Command with no Destination AddressThe most useful options are highlighted in yellow Some options do not work together such as the ndasht andndashn options Other options can be used together Experiment with the following optionsCCNA

This Packet Tracer activity demonstrates the ping and tracert commands from a host You will observe the steps of the operation of these commands in a network

671 Lab- Ping and Traceroute

This lab demonstrates the ping and tracert commands from a host You will observe the steps of the operation of these commands in a network


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