the eight steps - troubleshooting

8/17/2019 The Eight Steps - Troubleshooting

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The eight steps

The most important part of troubleshooting any problem is to divide the tasks of problem resolution into a

systematic process of elimination. Cisco has broken this process into eight steps:

1 Define the problem.

2 Gather detailed information.

3 Consider probable cause for the failure.

Devise a plan to solve the problem.

! "mplement the plan.

# $bserve the results of the implementation.

% &epeat the process if the plan does not resolve the problem.

' Document the changes made to solve the problem.

Top 10 Basic Network Troubleshooting Tools Every IT Pro Should Know

(et)ork troubleshooting tools are a necessity for every net)ork administrator. *hen getting started in the

net)orking field+ it is important to amass a number of tools that can be used to troubleshoot a variety of

different net)ork conditions.

*hile it is true that the the use of specific tools can be sub,ective and at the discretion of the engineer+ theselection of tools in this article has been made based on their generality and common use. This article revie)s

the top 1- basic tools that can help you troubleshoot most net)orking issues.

10 Ping

The most commonly used net)ork tool is the ping utility. This utility is used to provide a basic connectivity test

bet)een the reuesting host and a destination host. This is done by using the "nternet Control /essage 0rotocol

"C/0 )hich has the ability to send an echo packet to a destination host and a mechanism to listen for aresponse from this host. imply stated+ if the reuesting host receives a response from the destination host+ this

host is reachable. This utility is commonly used to provide a basic picture of )here a specific net)orking problem may e4ist. 5or e4ample+ if an "nternet connection is do)n at an office+ the ping utility can be used tofigure out )hether the problem e4ists )ithin the office or )ithin the net)ork of the "nternet provider. 5igure 1

belo) sho)s an e4ample of the ping utility being used to obtain the reachability status of the locally connected

router.



can potentially change often. The utilities that can be used to find out this "0 configuration information include

the ipconfig utility on *indo)s machines and the ifconfig utility on 7inu468ni4 based machines. 5igure 3 belo) sho)s an e4ample of the ifconfig utility sho)ing the "0 configuration information of a ueries host.

5igure 3: "fconfig utility

% Nslookup

ome of the most common net)orking issues revolve around issues )ith Dynamic (ame ystem D(address resolution issues. D( is used by everyone using the "nternet to resolve commonly kno)n domain

names i.e. google.com to commonly unkno)n "0 addresses i.e. %.12!.11!.1%. *hen this system does not

)ork+ most of the functionality that people are used to goes a)ay+ as there is no )ay to resolve this information.The nslookup utility can be used to lookup the specific "0 addresses associated )ith a domain name. "f this

utility is unable to resolve this information+ there is a D( issue. 9long )ith simple lookup+ the nslookup utility

is able to uery specific D( servers to determine an issue )ith the default D( servers configured on a host.

5igure belo) sho)s an e4ample of ho) the nslookup utility can be used to uery the associated "0 addressinformation.



5igure : (slookup utility

& Netstat

$ften+ one of the things that are reuired to be figured out is the current state of the active net)ork connections

on a host. This is very important information to find for a variety of reasons. 5or e4ample+ )hen verifying the

status of a listening port on a host or to check and see )hat remote hosts are connected to a local host on aspecific port. "t is also possible to use the netstat utility to determine )hich services on a host that is associated

)ith specific active ports. 5igure ! belo) sho)s an e4ample of the netstat utility being used to display the

currently active ports on a 7inu4 machine.

5igure !: (etstat utility

' PuTT("Tera Ter)



*hen connecting to a variety of different types of euipment+ a telnet+ or serial client is reuired; )hen

this is reuired both the puTT< and Tera Term programs are able to provide these functionalities. The selectionof one over the other is strictly a personal preference. 5igures # and % belo) sho) both puTT< and Tera Term

being used to connect to a host via .

5igure #: 0uTT<

5igure %: Tera Term



* Subnet and IP +alculator

$ne of the most important tools in the belt of a ,unior net)ork engineer is an "0 net)ork calculator. These can

be used to unsure a correct "0 address selection and )ith this a correct "0 address configuration. *hile this type

of tool is used by senior level net)ork engineers+ much of the information obtained from the tool becomessimpler to calculate the longer and more e4perience you have in the field. T)o of the more commonly used free

"0 calculators include *ildpackets =itcricket (et)ork Calculator and olar)inds 9dvanced ubnet Calculator

)hich can be found at the links belo).

http://www.bitcricket.com/downloads/IPCalculator.msi

http://downloads.solarwinds.com/solarwinds/Release/FreeTool/SolarWinds-Subnet-Calculator.zip

5igure ': ubnet calculator

, Speedtestnet"pingtestnet

9 very easy test that can be used to both determine the "nternet band)idth available to a specific host and to

determine the uality of an "nternet connection is the use of the tools available at the speedtest.net and

pingtest.net )ebsites. The speedtest.net site provides the ability to determine the amount of band)idth that isavailable to a specific host at a specific point in time; this is often a good tool to use )hen measuring ho) long







it is going to take to upload or do)nload information from a local to remote host. This measurement can also be

used to determine )hether the connection is offering the amount of band)idth that )as purchased from the"nternet provider; keep in mind ho)ever that some amount of band)idth difference is e4pected bet)een the

uoted band)idth purchased and the measured band)idth. The pingtest.net )ebsite is used to determine the

uality of the connection by measuring the ping response times and ,itter amounts over a short period of time.This information can be used to determine a likelihood of ho) )ell the measured connection )ill deal )ith

certain types of high demand traffic like >oice over "0 >o"0 or gaming. 5igure ? and 1- belo) sho) e4ample

output from both of these sites.

5igure ?: peedtest



5igure 1-: 0ingtest

- Pathping")tr

"n an effort to take advantage of the benefits of both the ping and tracert6traceroute commands+ the pathping and

mtr utilities )ere developed. =oth of these tools take the functionality and information that can be obtainedfrom these types of tools and provide a more detailed single picture of the path characteristics from a specific

host to a specific destination. 5igure 11 and 12 belo) sho) e4amples of these t)o tools and )hat information

they provide.



5igure 11: 0athping



5igure 12: /tr

1 .oute

The last of the tools covered in this article is the route utility. This utility is used to display the current status of

the routing table on a host. *hile the use of the route utility is limited in common situations )here the host only

has a single "0 address )ith a single gate)ay+ it is vital in other situations )here multiple "0 address andmultiple gate)ays are available. 5igure 13 belo) sho)s an e4ample of the route utility being used on a

*indo)s machine.

5igure 13: &oute @tility

Su))ary

9s )ith any ,ob+ the type of tools that are uickly available can greatly influence the amount of time that it takesto complete a ,ob. *hen troubleshooting a net)orking issue+ the amount of time that it takes to find and fi4 a

problem directly affect the )asted costs that it causes to any system relying on the net)ork. This article has



taken a look at the 1- most commonly used tools that can help in ensuring that the time that it takes to find and

fi4 a problem is as short as possible. " hope the information in this article can be helpful in futuretroubleshooting.

+isco Network Troubleshooting $or Beginners

=y telios 9ntoniou

9s a (et)ork Angineer+ your primary goal is to make sure that your net)ork euipment is operating properly at

all times. =ut )e all kno) that any euipment can break do)n. The reasons for this could be soft)areinconsistencies+ hard)are malfunctions+ maybe even environmental haBards.

@nder such unpredictable conditions+ your responsibility is to identify and isolate the cause of the malfunction

and correct it as soon as you can. Thats )hy it is e4tremely helpful to kno) some specific techniues that have been proven to be crucial and essential in the net)orking )orld.

"n todays article "ll present the most important commands that you )ill definitely find helpful and evenmandatory throughout your net)orking career and specifically during net)ork troubleshooting situations. The

commands " am talking about+ and )hich are truly invaluable+ are:

• Ping

• Traceroute

• Telnet

• Show inter$aces

• Show ip inter$ace

• Show ip route

• Show running/con$ig

• Show startup/con$ig

The Ping tility

The PIN co))and operates on the (et)ork layer and uses the services of the "C/0 protocol. "t is the first

command that you should use at the beginning of your troubleshooting process.

*ith 0"(G you can test )hether a remote host is alive by transmitting echo reuest messages and receive echoreplies from the specific host. eep in mind that even if a host is alive+ it does not mean that it is functioning

properly+ that is )hy 0"(G is used at the beginning of your investigation and is the best command to start )ith.

http://blog.pluralsight.com/author/stelios-antoniou




"ve covered 0"(G e4tensively in one of my previous posts+ so for more details on 0"(G+ check out: o) to

Troubleshoot <our Connections )ith 0ing and Traceroute.

0"(G command has uite a lot of options from )hich you can greatly benefit. 5or e4ample+ you can choose to

0"(G )ith different net)ork protocols. /oreover+ you are able to set the e4act number of 0"(G reuests to be

transmitted. <ou can also choose the length of data carried )ithin the echo reuest packet provided in bytes

and also specify )hether fragmentation of this packet is allo)ed or not during transmission. The last t)ooptions in cooperation can be used to identify the lo)est /T@ value e4isting in the communication path.

$n Cisco devices the simpler )ay to use the 0"(G utility is to issue the command 0"(G along )ith the "0

address of the remote device:

5or more advanced features+ simply issue the 0"(G command and follo) the prompts from that point on:

The Traceroute +o))and

The T.2+E.3TE co))and traces the endEtoEend path a packet takes though an internet)ork. imilarly

)ith 0"(G+ it uses the "C/0 protocol )ith TT7 timeouts to perform its operation.

9gain+ for more details on this command see o) to Troubleshoot <our Connections )ith 0ing and Traceroute.

http://blog.pluralsight.com/blog/how-to-troubleshoot-your-connections-with-ping-and-traceroute/2007-10-01/









This command is very useful in identifying potential link bottlenecks throughout the transmission path. ere is

a sample output of the T&9CA&$@TA command:

The Telnet +o))and

@se the telnet co))and to verify TC0 stack and application layer soft)are bet)een source and destination

stations. $f course+ to be able to telnet on a Cisco device+ the latter needs to be already configured to accepttelnet connections. To use TA7(AT ,ust issue the telnet command along )ith the "0 address or hostname of the

remote station:

The Show Inter$aces +o))and

The show inter$aces co))and presents all the available interfaces that can be configured on your Ciscodevice. <ou can e4plicitly use this command to sho) only details on a single interface by issuing the interfaces

name after the sho) interfaces command. This command is very useful because it can reveal layer 1 and layer 2

problems. /oreover+ this command provides details regarding the hard)are address /9C+ "0 address+

encapsulation method and statistics concerning erroneous conditions on the specific interface. A4amine theoutput of the show inter$ace $astethernet 0:



The first line of the sho) interface command is the most important one. The first parameter refers to the physical layer+ therefore

in this case 4astEthernet 0 is up and operating. The second part of the line refers to the Data 7ink 7ayer;

therefore here line protocol is up means that )e have layer 2 connectivity as )ell. There are four possibleoutputs that you may come across:

• 4astEthernet0 is up5 line protocol is up6 =oth the 0hysical and Data 7ink layers on the interface are

functioning correctly.

• 4astEthernet0 is down5 line protocol is down6 This output indicates a physical interface problem. 5or

e4ample+ the cable on this interface or on the remote interface is disconnected.

• 4astEthernet0 is up5 line protocol is down6 "n this case+ 0hysical layer is operational. The line protocol

being do)n indicates a clocking or framing problem. 0robable reasons for this are encapsulation and

clock rate mismatches.

• Ethernet0 is ad)inistratively down5 line protocol is down6 This output indicates that a local interface

has been manually shut do)n using the shutdo)n command.

The Show IP Inter$ace +o))and

The show ip inter$ace co))and )ill provide details regarding layer 3 configuration on the interfaces. @sing

this command you can see the "0 address and mask configured on a given interface+ )hether an access list is



applied on the interface as )ell as basic

"0 information.

The Show IP .oute +o))and

@se the show ip route co))and to find detailed information regarding the routes configured on the router.eep in mind that the router can only route packets to the net)orks listed in its routing table. "t is possible that a

router can not reach a net)ork you manually configured therefore+ that specific route is removed from its tableand that is )hy you should use the sho) running configuration command in con,unction )ith sho) ip route to

spot possible inconsistencies.

5or more details on "0 routing issues see my article on Default and tatic &outing =asics.

http://blog.pluralsight.com/blog/ip-addressing-and-routing-part-3-default-and-static-routing-basics/2007-11-15/

http://blog.pluralsight.com/blog/ip-addressing-and-routing-part-3-default-and-static-routing-basics/2007-11-15/



Show .unning/+on$ig and Show Startup/+on$ig +o))ands

"ssue the show running con$iguration co))and to find out the )hole configuration your Cisco devices use)hile operating. =y looking at the details of your devices+ configuration can help you identify the cause to your

problem. @se the show startup con$iguration co))and to see the configuration commands that )ill be

loaded to your device the ne4t time it reboots and compare it )ith your running configuration in order toidentify possible unconformities.

In the End 7 4ollow (our Instincts

"solating a net)ork malfunction is not an easy task. "n many cases you need to s)im into really deep )aters in

order to identify the error. /eaning+ that you )ill probably need to get into the bits and bytes in order to locate

the error.



9 lot of net)ork monitor tools are available to help you during these difficult tasks. 9nd although theres a lot

you can do+ remember to never lose your courage; have patience and follo) your gut.

ometimes the problem that youre searching for )ill be right in front of you and )ill slip out of your hands+

,ust )hen you think you have it. o be persistent+ be patient and remember: you )ill )in the battleF

=e prepared; in order to fight )ell+ you should be armed )ell. o get to kno) your device very )ell+ kno) ho)

it operates+ and kno) ho) to use the basic troubleshooting commands that you ,ust learned so that you can

identify the problem+ or at least estimate )here the problem might be. Good luck

8ow to Troubleshoot (our +onnections with Ping

and Traceroute

=y telios 9ntoniou

The PIN utility is one of the most famous and most helpful net)orking commands. "ts the first command that

comes to mind )hen facing net)ork reachability problems. "ts also the first command that needs to be issued

)hen there is a need to find out )hether a certain host is HaliveI or not.

The ping command uses the services of the "nternet Control /essage 0rotocol "C/0+ the latter beingencapsulated in the "0 header. Therefore+ the ping utility operates basically on layer 3 the (et)ork layer of the

$" model. "t does not use the services of the Transport layer+ and the reason for that is that traffic reliability

issues are not the case here. 0ing performs a simple host lookup.

T.2+E.3TE is another very helpful utility that operates similarly to ping and also uses the services of the"C/0 protocol. Traceroute+ as the name implies+ is used to trace the path bet)een the sender and the destination

host. "t is a oneE)ay trace+ meaning that it traces the route from the source to destination and not the other )ay

around+ )hich by the )ay+ may follo) a different path. Traceroute also uses the services of @ser Datagram0rotocol @D0+ in specific implementations+ as the transport layer for a specific reason that )ell go into

further on.

o first+ lets start )ith an overvie) of "C/0 protocol and then )e can get into the details of ho) ping and

traceroute use this protocol to perform their tasks.

Internet +ontrol 9essage Protocol :I+9P;

"C/0 is a (et)ork layer protocol that belongs to the group of control protocols similar to 9&0 and &9&0.

"C/0 protocol has been designed )ith the unreliable characteristics of the "0 protocol in mind. Due to thisunreliability and connectionless behavior of "0+ there )as no )ay of informing the originator host that

something )ent )rong during data transmission. "C/0 has been designed to provide this function.

"C/0 messages report back to the sender )hen something une4pected occurs+ giving the person a clue of )hat

might have gone )rong. " )ant to remind you that "C/0 does not solve the reliability issues of "0; that is up tothe upper layer the Transport layer to perform. "C/0 messages are encapsulated in "0 packets as seen belo):





"mage 1: "C/0 Ancapsulation

"C/0 messages use the follo)ing format:

"mage 2: "C/0 /essage 5ormat

The most important "C/0 message types are listed belo):

"mage 3: "mportant "C/0 /essage Types

Troubleshooting with PIN

7ets take a look at the behavior of the ping command )ith the help of Athereal application. 5irst+ to launch the

ping command the simplest )ay is to open a command prompt )indo) and type in PIN <ip address o$ the

host to reach=+ or if D( service is running type in PIN <.> o$ the destination host=. ometimes+ thee4tended ping command+ )hich issues continuous echo reuest messages+ is very helpful. The format of this

command is PIN ?t <IP address o$ the host=. The ping command operates the same )ay in *indo)s+ @ni4+

Cisco machines and in every other net)orking device. The principle is the same+ even though variations on the

e4tended functions of the command may e4ist.



"n the ne4t image you can see a ping command to)ards the @&7 of Trainsignal.com. D( uery is performed

first to translate the @&7 to an "0 address+ and then four echo reuest message types are transmitted. Transmit packets are time stamped. *hen the remote host receives these echo reuests+ inside the echo reply messages it

includes the timestamp enclosed in the echo reuest. @pon receiving the reply message and performing simple

calculations+ the round trip delay time is revealed and noted:

"mage : A4ecuting the 0ing Command

7ooking at the Athereal trace+ you can see that the echo reuest "C/0 message has the type field value set to '.

This is the standard value for echo reuest messages. 9lso notice that the TT7 field has the value of 12'

Common value for *indo)s platforms. This value indicates the number of hops the packet is allo)ed totraverse before getting dropped. This value+ due to scattering of net)orks+ should have a great value J anything

above #. Cisco machines use a TT7 value of 2!#.



"mage !: Acho &euest /essage Ancapsulation

=elo) you can see one of the echo reply messages as captured by Athereal tool. "t can be seen that the "C/0

echo reply message has a type value - Bero:

"mage #: Acho &eply /essage Ancapsulation



Troubleshooting with T.2+E.3TE

The traceroute command operates similarly to ping. $n Cisco routers and @ni4 platforms the layout of the

command is: T.2+E.3TE <destination IP address= or T.2+E.3TE <.> o$ the destination host=.

$n *indo)s machines the function of traceroute comes )ith the command T.2+E.T short for trace route+)hich operates in a slightly different manner than in Cisco and @ni4 platforms details on this are belo).

Traceroute uses a clever )ay to capture the footprint of a packets ,ourney. *e )ill use an imaginary e4ample

see the ne4t image to help us investigate ho) traceroute achieves its purpose:

• .outer2 prepares an "C/0 echo reuest message+ encapsulates it in an "0 packet having ource

addressK1%2.1#.1.1+ Destination addressK1?2.1#'.%.2 )ith TimeEToE7ive TT7 valueK1+ Destination

@D0 portK anything not used usually greater than 3---- and for)ards it.

• .outerB+ upon receiving this packet+ decrements one unit from TT7 value+ hence TT7 becomes -+

)hich means that it has to drop this packet. "t replies back to the sender )ith an "C/0 Time e4ceeded

message+ including its source address in the 9 field of the "0 header 9K1%2.1#.1.2.

• .outer2 receives the response and prints out on the screen the first hop "0 addressK1%2.1#.1.2.

• 9fter)ars+ .outer2 sends the same echo reuest message )ith TT7 valueK2.

• .outerB decrements it by one and for)ards it to &outerC )hich decrements by one again TT7K-+

forcing it to return an "C/0 time e4ceeded message )ith 9K1?2.1#'.1.2.

• .outer2 no) prints out the second hop on screen "0 addressK1?2.1#'.1.2.

• 5inally .outer2 sends an "C/0 echo reuest )ith TT7 valueK3 )hich is terminated on .outer@. The

latter passes the packet to the transport layer )here the )rong @D0 port number causes .outer@ toissue an "C/0 0ort @nreachable message.

• .outer2 upon receiving this message from .outer@ kno)s that it has reached the final hop )hich

prints out on screen and stops sending any more messages.



"mage %: Traceroute A4ample

2 .eal EAa)ple o$ Traceroute

(o) that )e understand ho) traceroute )orks+ lets see ho) it behaves in a real situation. @sing command

prompt under *indo)s host+ T&9CA&T to ))).trainsignal.com is issued. The result is sho)n in the image

belo):

http://www.trainsignal.com/

http://www.trainsignal.com/



"mage ': 0rintout of T&9CA&T Command

=y looking at the image above+ you can see that each "C/0 echo reuest message is repeated three times beforethe sender increments the TT7 value and resend the reuest message. The three round trip delay times for all

three messages are included at the beginning of each hop. 9 couple of reuest timed out messages come from

routers that are configured not to respond to "C/0 echo reuest messages.

The image belo) sho)s the content of the echo reply message received from trainsignal.com message number

2- as sho)n on figure '. 9lthough )e )ould e4pect an "C/0 message )ith type valueK3 0ort @nreachable+ aTT7 e4ceeded message typeK11 is received. This difference comes from the fact that in *indo)s platforms

@D0 ports are not used.

"mage ?: Time A4ceeded /essage from Destination ost

The *indo)s platforms+ upon receiving an echo reply message from the final destination+ issue three more echoreuest messages to that host; hence the last noted echo reply message on in the iamge above.

hat +an Ping and Traceroute @o $or (ouC

0ing and traceroute commands can be very helpful J if used appropriately. @se the 0"(G command )hen thee4istence of a host is )hat interests you. @se T&9CA&$@TA in Cinsco and @ni4 or T&9CA&T in *indo)s to

get an idea of )hat route your packets take to reach their destination.



Top % T+P"IP tilities Every Networking Pro

Should Know

=y &oman &afacB

"f youre planning on pursuing a field in net)orking or ,ust looking to e4pand your net)orking kno)ledge then

this article is for you. TC06"0 utilities are essential J not only )ill they help you on your net)orking e4ams butyoull be able to diagnose most TC06"0 problems and begin )orking on solutions.

The top % tools that " )ill talk about today include: 0ing+ Tracert+ 9&0+ (etstat+ (btstat+ (7ookup+ and

"0config. These tools )ill help you to check the status of your net)ork and allo) you to troubleshoot and testconnectivity to remote hosts.

<ou use these utilities in Dos and you get there by clicking on Start+ going to .un and typing c)d.

ere are the top % TC06"0 utilities and their functions.

1 Ping

The 0"(G utility tests connectivity bet)een t)o hosts. 0"(G uses a special protocol called the "nternet Control

/essage 0rotocol "C/0 to determine )hether the remote machine )ebsite+ server+ etc. can receive the test

packet and reply.

9lso a great )ay to verify )hether you have TC06"0 installed and your (et)ork Card is )orking.

*ell start by 0inging the loopback address 12%.-.-.1 to verify that TC06"0 is installed and configuredcorrectly on the local computer.

Type: PIN 1-%001

http://blog.pluralsight.com/author/roman-rafacz

http://blog.pluralsight.com/blog/a-short-guide-to-internet-control-protocols/2007-09-20/


http://blog.pluralsight.com/author/roman-rafacz





This tells me that TC06"0 is )orking as )ell as my (et)ork Card.

To test out connectivity to a )ebsite all you have to do is type: ping espnco)

The results should tell you if the connection )as successful or if you had any lost packets.

0acket loss describes a condition in )hich data packets appear to be transmitted correctly at one end of a

connection+ but never arrive at the other. *hyL *ell+ there are a fe) possibilities.

The net)ork connection might be poor and packets get damaged in transit or the packet )as dropped at a router

because of internet congestion. ome "nternet *eb servers may be configured to disregard ping reuests forsecurity purposes.

(ote the "0 address of espn.com J 1??.1'1.132.2!-. <ou can also ping this address and get the same result.



o)ever+ 0ing is not ,ust used to test )ebsites. "t can also test connectivity to various servers: D(+ DC0+

your 0rint server+ etc. 9s you get more into net)orking youll realiBe ,ust ho) handy the 0ing utility can be.

- Tracert

Tracert is very similar to 0ing+ e4cept that Tracert identifies path)ays taken along each hop+ rather than the time

it takes for each packet to return ping.

"f " have trouble connecting to a remote host " )ill use Tracert to see )here that connection fails. 9nyinformation sent from a source computer must travel through many computers 6 servers 6 routers theyre all the

same thing+ essentially before it reaches a destination.

"t may not be your computer but something that is do)n along the )ay. "t can also tell you if communication isslo) because a link has gone do)n bet)een you and the destination.

"f you kno) there are normally routers but Tracert returns ' responses+ you kno) your packets are taking anindirect route due to a link being do)n.

, 2.P

The 9&0 utility helps diagnose problems associated )ith the 9ddress &esolution 0rotocol 9&0.





TC06"0 hosts use 9&0 to determine the physical /9C address that corresponds )ith a specific "0 address.

Type arp )ith the ? a option to display "0 addresses that have been resolved to /9C addresses recently.

* Netstat

(etstat (et)ork tatistics displays net)ork connections both incoming and outgoing+ routing tables+ and a

number of net)ork interface statistics.

"t is an important part of the (et)ork M e4am but its a helpful tool in finding problems and determining the

amount of traffic on the net)ork as a performance measurement.

http://blog.pluralsight.com/blog/free-video-training/comptia-network-training-videos/

http://blog.pluralsight.com/blog/free-video-training/comptia-network-training-videos/



Netstat ?s provides statistics about incoming and outgoing traffic.



' Nbtstat

(btstat (et=ios over TC06"0 enables you to check information about (et=ios names.

"t helps us vie) the (et=ios name cache nbtstat Ec )hich sho)s the (et=ios names and the corresponding "0

address that has been resolved nbtstat Er by a particular host as )ell as the names that have been registered by

the local system nbtstat n.

& NS>ookup

(7ookup provides a commandEline utility for diagnosing D( problems. "n its most basic usage+ (7ookupreturns the "0 address )ith the matching host name.



% IP+on$ig

(ot part of the TC06"0 utilities but it is useful to sho) current TC06"0 settings.

The "0Config command line utility )ill sho) detailed information about the net)ork you are connected to. "talso helps )ith reconfiguration of your "0 address through release and rene).

7ets say you )ant to kno) )hat youre "0 address is J ipcon$ig is )hat you type in the command prompt.

ipcon$ig )ill give a uick vie) of you "0 address+ your subnet mask and default gate)ay.



ipcon$ig "all )ill give you more detailed information.

Through ipcon$ig "all )e can find D( severs+ if )e have DC0 enabled+ /9C 9ddress+ along )ith other

helpful information. 9ll good things to kno) if )e have trouble getting connected to the internet.

$ther "0Config tools that are helpful include ipcon$ig "release and ipcon$ig "renew. =ut before " get into thislets discuss ho) )e actually get an "0 9ddress.

There are t)o )ays to obtain an "0 address. $ne )ay is to have a static "0 address )hich )e manually assign.The second one is to have a dynamic "0 address obtained through a DC0 server.

"f you )ere to right click on (et)ork Connects+ go to 0roperties+ right click on 7ocal 9rea Connection+ scrolldo)n to "nternet 0rotocol TC06"0+ and select 0roperties J youll see t)o options:

• $btain an "0 address automatically

• @se the follo)ing "0 address



@nless you kno) your static "0 address youll )ant to stick to the option for automatically obtaining the "0

address. "f you have it set to automatic your computer )ill be issued an "0 through a DC0 server.

9nd ,ust in case youre )ondering+ Dynamic ost Configuration 0rotocol DC0 is a net)ork protocol that

enables a server to automatically assign an "0 address to a computer from a defined range of numbers i.e.+ ascope configured for a given net)ork.

"n laymens terms: " have a cable modem at home and " have that modem connected to a )ireless router that

issues out "0 address to anyone that connects to that router. That is DC0 that is issuing out "0 addresses.

<our company probably has a server dedicated to this. @nderstanding this is definitely important for anynet)orking e4am.

7ets look at )hat happens )hen )e release our "0 address.






"ve ,ust lost internet connection and my "0 address is -.-.-.-. "f " type ipconfig 6rene) this option reEestablishes

TC06"0 connections on all net)ork adapters and " can resume my internet surfing.

Note6 ipconfig 6release rene) )ont )ork if you manually assigned your "0 addresses.

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