In this video,
we're going to discuss some other issues you may need
to troubleshoot,
things like low optical link budgets,
certificate issues, license feature issues,
BYOD challenges and hardware failures.
First, let's talk about low optical link budgets.
And what exactly is an optical link budget?
Now, an optical link budget is a calculation
that considers all the anticipated losses
along the length of a fiber optic connection.
This is important to understand,
because the light signal
that's going across that fiber optic cable,
will lose signal strength as it travels down this cable.
Now, this occurs naturally due to the distance of the cable,
as well as from losses due to multiplexing,
bends in your cable, imperfect connections,
patches or splices that happen along the fiber optic cable.
If you experience a low optical link budget,
your fiber connection will experience issues,
such as reduced transmission efficiency,
slower connection speeds,
or even downtime on that connection.
To measure the condition of your fiber optic connection,
you're going to use an optical time-domain reflectometer
to measure the amount of losses or reflections
that are occurring in the connection.
This reading from the optical time-domain reflectometer,
is going to be reported in decibels per kilometer.
And this indicates
how much attenuation and degradation is occurring
over the length of that connection.
Normally, you should experience 0.25 decibels per kilometer
for a standard fiber optic cable.
But if you experience a higher rate than this,
then you may have a low optical link budget.
To calculate your link budget,
you simply take the receiver's power budget,
or how much initial signal you're going to be transmitting out
and then you subtract any multiplexing
and demultiplexing losses,
as well as losses from the fiber itself
that's caused by those distances and the imperfections
and any losses from the connectors or patch panels
that are being used as well.
Now, this will give you the total optical link budget.
For example, let's say I designed a fiber optic circuit
with a receiver that can sense light received
between negative-seven decibels and negative-23 decibels.
And I send the signal out at positive-five decibels.
Now, if I only have a loss of 20 decibels
due to the distance,
the connectors and a splice in that cable,
the receiver's going to be able to pick up that signal,
because I still have negative-15 decibels
of light signal being received at that distant end.
And negative-15 is in between negative-seven
and negative-23.
On the other hand, if the fiber connection was broken
and somebody went to repair it by splicing that connection,
maybe they did a really bad job of it
and it adds an extra 25 decibels of signal loss.
Now, I'm going to transmit at the same five decibels
that I was before,
but I'm losing 15 decibels
for distance and that first splice.
And now, because of this poor second splice,
I'm losing another 25 decibels.
This brings my total value on the receiving end
to negative-35 decibels.
And that means the receiver can't pick up that signal,
because it can only sense the signals
between negative-seven and negative-23 decibels.
And negative-35 is far too weak for the receiver to see it.
Now, we're going to have a broken fiber link essentially,
because we have a low optical link budget level.
So what can we do to fix this?
Well, we can either increase the power of the transmitter
to say plus-20 decibels instead of plus-five decibels,
or we can have somebody go back
and try to do a better job of splicing that cable.
Now, this isn't a very realistic example.
Because most professional splices will only cost a loss
of 0.1 or 0.2 decibels.
But hopefully, you're getting the idea
of how a low optical link budget can work
and negatively affect your fiber networks.
Next, we have certificate issues
that can cause network issues for us as well.
A digital certificate is used as a credential
to facilitate the verification of identities
between users inside of a transaction.
For example, when you attempt to connect
to an e-commerce site over HTTPS,
your network client uses digital certificates
to validate the server's identity
and decide if it can really trust that server
when sending sensitive information over to it.
The most common certificate issues are going to occur
on a website's SSL or TLS certificate
when it's displaying as untrusted.
Now, this occurs for one of three reasons.
It can be that the digital certificate is not signed
by a trusted certificate authority,
the certificate itself has already expired,
or the server didn't have a certificate associated
with a trusted root certificate.
Now, regardless of which of these three things is happening,
the end result is going to be the same.
Your client's browser is not going to show a secure connection
over HTTPS,
because its web browser and the server are not communicating
over a secure tunnel.
Now, in either of these cases,
you can't solve the issue for your network clients.
Because you don't own that web server.
But if you were the one who owned that web server,
then it becomes your problem to fix.
Now, in this case,
you need to purchase a digital certificate
from a trusted certificate authority and install it,
or you need to renew your expired digital certificate,
or you need to install a certificate
from a trusted certificate authority
with a valid root certificate on your server.
In addition to using digital certificates
with HTTPS websites,
we also can use digital certificates inside of our networks
for network authentication using 802.1X with EAP.
In these cases,
your security team's,
going to run your organization's own certificate authority
to create these digital certificates
and issue them to the network clients and the servers.
Again, if you're having issues
with these digital certificates,
you need to ensure they're trusted,
that they're not expired
and that they're installed properly
on the network devices and the network clients.
Next, we need to talk about license feature issues
that could arise in your networks.
Sometimes, when troubleshooting issues in your network,
you may come across an error message,
such as "Error, feature not licensed."
Now, as you can see in this example
from a NetScaler VPX appliance,
there are many different features
that are enabled or disabled,
based upon the license
that's been purchased by this organization.
For example, the license they have purchased will allow them
to do load balancing and content switching.
But it does not support global server load balancing,
or clustering.
This is a different feature set
that requires a different and more expensive license.
Now, if you get an error,
concerning a particular license feature
in this or another network device,
you first need to determine
what license you have loaded on that device.
Then compare the license you loaded
with the features it unlocks.
If the license is not unlocking the features you expected,
you may need to contact the manufacturer
to troubleshoot the issue.
But you may realize, you simply purchased the wrong license
for the features that you need.
And in this case,
you need to work with your organization's purchasing agents
and their contracting professionals
to get the right license procured,
so you can load it up into the device.
Now, this is a common issue
in large bureaucratic organizations
where the people,
who use the things and install the devices,
are not the same ones,
who are empowered to make purchasing decisions.
As a young network administrator,
I remember submitting the requisition forms
to my organization for all the licenses I needed.
I specified that I needed the platinum license.
And the contracting person decided,
"You know what?
The gold license would be just fine,
because it costs 35% less."
Well, guess what?
That contracting person didn't know
that a gold license,
didn't include the three critical features
that we actually needed.
And those features were the whole reason,
we were buying this particular network appliance.
So when we received the license key
and we tried to load it up on the network appliance,
we kept getting the "Feature not licensed" error message.
And it took us almost two days to figure out
that the reason was our organization gave us a gold license
and not a platinum license that we really needed.
So learn from our mistake,
make sure you tell the contract personnel
that substitutions are simply not allowed.
You need this level of license,
or it just won't work for the features you need.
Next, let's discuss BYOD challenges,
or Bring-Your-Own-Device challenges.
Now, I don't want to specifically focus
on security challenges associated with BYOD policies.
Instead, I really want to focus on the networking issues
that you may come across
when you're trying to support a BYOD policy
inside your organization.
Now, BYOD or Bring Your Own Device is this policy
that allows your end users
to bring their own smartphones, tablets, laptops
and other technical devices into work
and use them on your organization's network.
Now, BYOD allows the organization to save money
by not having to purchase all these devices
for the employees.
But instead, they're relying on the employees
to bring their own equipment and their own devices
and then do the business
on those devices using your organization's network.
Now, the biggest challenge with BYOD,
besides securing these devices,
is actually supporting these devices.
When a user brings their own device,
you're no longer supporting one or two models of laptops.
But instead,
you've got 50 or a 100 or 200 different varieties now.
Your employees may bring a Windows 10 Home Edition laptop,
or a MacBook Air or a Chromebook.
And guess what?
You're going to be expected to support all of them.
This is a massive headache and a huge challenge
for support personnel,
like our service desk and our network technicians.
Now, when a device doesn't work properly,
like we want to expect it to,
we have to determine is it the device,
or is it some software the user loaded,
or is it a network issue that we need to solve?
This makes it very challenging.
Honestly, while many organizations think
that implementing a BYOD policy can save them a lot
of money,
because they'll have a reduced capital expenditure
or CapEx cost,
it really just increases your OpEx,
or operational expenditures.
Because now, you're wasting so much time on labor hours
to support and troubleshoot all these different devices.
Another challenge with supporting these devices,
is ensuring the security of your network
and how these devices are going to access your network.
Are you going to let these devices connect
on your wired network connections,
or are you going to make them use wireless?
Will you require that they be registered ahead of time,
so you know what their MAC addresses are
and they can be identified in whitelist,
or are you going to require these BYOD devices
to remain on a separate VLAN?
That way,
they're not going to touch your internal network services
and if they do,
they have to pass through a screened subnet.
All of these are valid questions to consider
as you determine how you're going to support BYOD
on your network,
both operationally
and from a troubleshooting and repair perspective.
Finally, let's talk about hardware failures.
Hardware failures can occur all over your network,
your routers, your switches and your firewalls can fail
for all sorts of reasons,
just like your network clients can.
As you begin to troubleshoot this issue,
you need
to pinpoint both which device is experiencing the failure
and which component on the device has failed.
Once you identify the device that failed,
such as a router that isn't passing traffic
from one subnet to another,
you then need to identify the component that failed.
Most components
on our network devices are field-replaceable,
which means you can swap them out with different components
and get the device back up and operational very quickly.
For example,
if we had one of our dual power supplies fail
in a border router,
we can schedule an emergency maintenance window,
we can power down the device, open up the chassis,
replace the broken power supply
and then return the device to normal operations.
If an interface card or module is broken or defective,
we can simply replace that as well.
And many of these are considered hot pluggable modules.
So if you have an SFP+ module that fails,
we can simply replace it
without even shutting down the network device,
or taking it offline.
If a client or server on the other hand is found
to have a defective component or hardware failure,
we can work with our CompTIA A+ technicians
to solve those issues
by replacing the associate hardware components.
Normally, with a defective or failed piece of hardware,
the fastest way to restore service is simply
to replace the component that's failed us.
In some cases,
such as a failed motherboard on a router or switch,
you may need to replace the entire device.
In these cases,
you should get a spare switch or router
from your supply closet,
mount it into the rack,
load up your backup configurations from the failed device
and put that into the replacement device
and then reconnect all the cables to it
and finally, restore service using your new device.
Then you could take the failed device out of the rack,
return it to the manufacturer for repair
and then it can become part of your spares in the future
if it's under warranty,
or you could dispose of it properly
if it's reached the end of its useful life.