0:00:01.550,0:00:03.260
when you're troubleshooting complex

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network problems you may find that the

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resolution is not as obvious as you

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might hope in this video we're gonna

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step through a methodology that should

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help you troubleshoot any problem you

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run into this is the flow chart of that

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network troubleshooting methodology and

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we're going to step through each section

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of this flow and describe how it can

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help you solve those really difficult

0:00:24.980,0:00:27.619
problems the first thing you want to do

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is identify the problem this may not be

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as straightforward as you might think we

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first need to collect as much

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information as possible about the issue

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that's occurring in the best possible

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scenario you'll be able to duplicate

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this problem on demand this will help

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later as we go through a number of

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testing phases to make sure that we're

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able to resolve this issue when a

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problem happens on the network it

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usually affects more than one device and

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sometimes it affects those devices in

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different ways you want to be sure to

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document all of the symptoms that may be

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occurring even if they are very

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different between different devices you

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may find that a single problem is

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causing all of these different systems

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across these different devices many

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times these issues will be identified by

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the end users so they may be able to

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provide you with a lot more detail of

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what's really happening you should

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question your users to find out what

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they're seeing and if any error messages

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are appearing in this course we've

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already discussed the importance of the

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change control process and knowing

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exactly what is changing in your

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environment without some type of formal

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change control process someone may be

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able to make an unscheduled change that

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would affect many different people so

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when an error or network problem occurs

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you may want to find out what was the

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last thing that changed on this network

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that could have affected all of these

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users there's also going to be times

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when you're examining a number of

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different problems that may not actually

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be related to each other it's always

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best to separate all of these different

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issues out so that you can approach and

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try to resolve each issue individually

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now that you've collected as much

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information as possible

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you can examine all of these details to

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begin establishing a theory of what you

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think might be going wrong since the

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simpler explanation is often the most

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likely reason

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for the issue that may be a good place

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to start but of course you'll want to

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consider every possible thing that might

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be causing this issue maybe start with

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things that aren't completely obvious

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you could start from the top of the OSI

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model with the way the application is

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working and work your way to the bottom

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or you may want to start with the bottom

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with the cabling and wiring in your

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infrastructure and work your way up from

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there you'll want to list out every

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possible cause for this problem your

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list might start with the easy theories

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at the top but of course include all of

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the more complex theories in this list

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as well now that we have a list of

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theories on how to resolve this issue we

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can now test those theories we may want

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to go into a lab and if we are able to

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recreate this problem in the lab then we

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can apply each theory until we find the

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one that happens to resolve the issue if

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you tried the first theory you may want

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to reset everything and try the second

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theory or the third and if you run out

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of theories you may want to go back and

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think of other things that might be

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causing this problem this might be a

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good time to bring in an expert who

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knows about the application or the

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infrastructure and they can give some

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theories and possible resolutions to

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test in the lab once you've tested a

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theory and found that the theory is

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going to resolve this issue you can then

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begin putting together a plan of action

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this is how you would implement this fix

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into a production network you want to be

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sure that you're able to do this with a

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minimum amount of impact to the

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production network and sometimes you

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have to do this after-hours when nobody

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else is working on the network you want

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to be able to implement this with a

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minimum amount of impact to production

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traffic so often you'll have to do this

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after hours my best practice is to

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document the exact steps that will be

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required to solve this particular

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problem if it's replacing a cable then

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the process will be relatively

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straightforward but if you're upgrading

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software in a switch a router or a

0:04:08.989,0:04:11.750
firewall there may be additional tasks

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involved in performing this plan of

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action you'll also want some

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alternatives if your plan doesn't go as

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designed for example you may run into

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problems when upgrading the software in

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a firewall so you may need an additional

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firewall or a way to roll back to the

0:04:26.150,0:04:27.250
previous version

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now that you

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documented your plan of action you can

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take that to your change control team

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and they can give you a window when you

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can implement that change the actual

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fixing of the issue is probably going to

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be during off-hours during non

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production times and you may need to

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bring in other people to assist

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especially if your window is very small

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once you have executed on your plan of

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action your job isn't done yet

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we need to make sure that all of these

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changes actually resolve the problem so

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now that the changes have been

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implemented we now need to perform some

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tests we may want to bring in the end

0:05:01.190,0:05:03.139
users who first experienced this problem

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so that they can run through exactly the

0:05:05.719,0:05:07.789
same scenario to tell you if the problem

0:05:07.789,0:05:09.620
is resolved or if the problem still

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exists this might also be a good time to

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implement some preventive measures that

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way we can either be informed that the

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problem is occurring or we can provide

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alternatives that we can implement if

0:05:20.569,0:05:23.719
that problem happens again after the

0:05:23.719,0:05:25.430
problem has been resolved this is a

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perfect time to document the entire

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process from the very beginning to the

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very end you'll of course want to

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provide as much information as possible

0:05:33.379,0:05:35.779
so if somebody runs into this issue

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again they can simply search your

0:05:37.940,0:05:40.159
knowledgebase find that particular error

0:05:40.159,0:05:42.050
that popped up and know exactly the

0:05:42.050,0:05:44.529
process you use to solve this last time

0:05:44.529,0:05:47.539
many organizations have a help desk with

0:05:47.539,0:05:49.250
case notes that they can reference or

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you might have a separate knowledgebase

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or wiki that you create where you're

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storing all of this important

0:05:54.440,0:05:57.349
information for the future a document

0:05:57.349,0:05:58.969
that was created a number of years ago

0:05:58.969,0:06:00.919
but still shows the importance of

0:06:00.919,0:06:02.900
keeping this documentation over time is

0:06:02.900,0:06:04.430
from Google research where they

0:06:04.430,0:06:06.830
documented the failure trends in a large

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disk drive population and because they

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were keeping extensive data over a long

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period of time they were able to tell

0:06:13.789,0:06:16.250
when a drive was starting to fail based

0:06:16.250,0:06:17.990
on the types of errors that they were

0:06:17.990,0:06:20.360
receiving being able to store all of

0:06:20.360,0:06:22.039
this important information and being

0:06:22.039,0:06:23.990
able to go back in time to see what

0:06:23.990,0:06:26.270
happened becomes a very important part

0:06:26.270,0:06:28.629
of maintaining a network for the future

0:06:28.629,0:06:31.159
let's summarize this troubleshooting

0:06:31.159,0:06:33.050
methodology we start with gathering as

0:06:33.050,0:06:35.449
much information as possible asking

0:06:35.449,0:06:37.190
users about what they're seeing and

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documenting any specific error messages

0:06:39.500,0:06:41.330
then we want to be able to create a

0:06:41.330,0:06:42.050
number of

0:06:42.050,0:06:43.789
series that might solve this particular

0:06:43.789,0:06:46.759
problem and once we have this list we

0:06:46.759,0:06:48.379
want to be able to put it in the lab and

0:06:48.379,0:06:50.389
try testing each one of these theories

0:06:50.389,0:06:52.340
until we find the one that actually

0:06:52.340,0:06:55.009
resolves the issue from there we can

0:06:55.009,0:06:57.169
create a plan of action and document any

0:06:57.169,0:06:59.599
possible problems that might occur we

0:06:59.599,0:07:01.280
can then get a time to implement the

0:07:01.280,0:07:03.530
issue and put it into our production

0:07:03.530,0:07:05.659
environment and then we can verify and

0:07:05.659,0:07:07.789
test and make sure that the entire

0:07:07.789,0:07:10.729
system is now working as expected and of

0:07:10.729,0:07:12.199
course finally we want to document

0:07:12.199,0:07:14.780
everything that we did from the very

0:07:14.780,0:07:16.729
beginning of our troubleshooting process

0:07:16.729,0:07:20.889
all the way through to the end

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you