-: Other issues. 2 2
In this video we're going to discuss some other issues 3 3
you may need to troubleshoot. 4 4
Things like low optical link budgets, certificate issues, 5 5
license feature issues, BYOD challenges 6 6
and hardware failures. 7 7
First, let's talk about low optical link budgets. 8 8
And what exactly is an optical link budget? 9 9
Now an optical link budget is a calculation that considers 10 10
all the anticipated losses along the length 11 11
of a fiber optic connection. 12 12
This is important to understand. 13 13
Because the light signal that's going across 14 14
that fiber optic cable will lose signal strength 15 15
as it travels down this cable. 16 16
Now this occurs naturally due to the distance of the cable, 17 17
as well as from losses due to multiplexing, 18 18
benzing your cable, imperfect connections, patches 19 19
or splices that happen along the fiber optic cable. 20 20
If you experience a low optical link budget, 21 21
your fiber connection will experience issues 22 22
such as reduced transmission efficiency, 23 23
slower connection speeds 24 24
or even downtime on that connection. 25 25
To measure the condition of your fiber optic connection, 26 26
you're going to use an optical time domain reflectometer 27 27
to measure the amount of losses or reflections 28 28
that are occurring in the connection. 29 29
This reading from the optical time domain reflectometer 30 30
is going to be reported in decibels per kilometer. 31 31
And this indicates how much attenuation and degradation 32 32
is occurring over the length of that connection. 33 33
Normally, you should experience 0.25 decibels per kilometer 34 34
for a standard fiber optic cable. 35 35
But if you experience a higher rate than this, 36 36
then you may have a low optical link budget. 37 37
To calculate your link budget. 38 38
You simply take the receiver's power budget or how much 39 39
initial signal you're going to be transmitting out, 40 40
and then you subtract any multiplexing and demultiplexing 41 41
losses as well as losses from the fiber itself 42 42
that's caused by those distances and the imperfections. 43 43
And any losses from the connectors or patch panels 44 44
that are being used as well. 45 45
Now, this will give you the total optical link budget. 46 46
For example, let's say I designed a fiber optic circuit 47 47
with a receiver that can sense light received between 48 48
negative seven decibels and negative 23 decibels. 49 49
And I send the signal out at positive five decibels. 50 50
Now, if I only have a loss of 20 decibels 51 51
due to the distance, the connectors 52 52
and a splice in that cable. 53 53
The is going to be able to pick up that signal 54 54
because I still have negative 15 decibels of light signal 55 55
being received at that distant end. 56 56
And negative 15 is in between negative seven 57 57
and negative 23. 58 58
On the other hand, if the fiber connection was broken 59 59
and somebody went to repair it by splicing that connection, 60 60
maybe they did a really bad job of it. 61 61
And adds an extra 25 decibels of signal loss. 62 62
Now I'm going to transmit at the same five decibels 63 63
that I was before. 64 64
But I'm losing 15 decibels for distance 65 65
in that first splice. 66 66
And now because of this poor second splice, 67 67
I'm losing another 25 decibels. 68 68
This brings my total value on the receiving end 69 69
to negative 35 decibels. 70 70
And that means the receiver can't pick up that signal 71 71
because it can only sense the signals between negative seven 72 72
and negative 23 decibels. 73 73
And negative 35 is far too weak for the receiver to see it. 74 74
Now, we're going to have a broken fiber link essentially, 75 75
because we have a low optical link budget level. 76 76
So, what can we do to fix this? 77 77
Well, we can either increase the power of the transmitter 78 78
to say plus 20 decibels instead of plus five decibels. 79 79
Or we can have somebody go back and try to do a better job 80 80
of splicing that cable. 81 81
Now, this isn't a very realistic example 82 82
because most professional splices will only cause a loss 83 83
of 0.1 or 0.2 decibels. 84 84
But hopefully you're getting the idea of how low optical 85 85
link budget can work and negatively affect 86 86
your fiber networks. 87 87
Next, we have certificate issues 88 88
that can cause network issues for us as well. 89 89
A digital certificate is used as a credential 90 90
to facilitate the verification of identities 91 91
between users inside of a transaction. 92 92
For example, when you attempt to connect 93 93
to an e-commerce site over HTTPS, 94 94
your network client uses digital certificates 95 95
to validate the server's identity and decide 96 96
if it can really trust that server when sending sensitive 97 97
information over to it. 98 98
The most common certificate issues are going to occur 99 99
on a websites SSL or TLS certificate 100 100
when it's displaying as untrusted. 101 101
Now, this occurs for one of three reasons. 102 102
It can be that the digital certificate is not signed 103 103
by a trusted certificate authority, 104 104
the certificate itself has already expired 105 105
or the server didn't have a certificate associated 106 106
with a trusted route certificate. 107 107
Now, regardless of which of these three things is happening, 108 108
the end result is going to be the same. 109 109
Your client's browser is not going to show a secure 110 110
connection over HTTPS because it's web browser 111 111
and the server are not communicating over a secure tunnel. 112 112
Now, in either of these cases, 113 113
you can't solve the issue for your network clients 114 114
because you don't own that web server. 115 115
But if you were the one who owned that web server, 116 116
then it becomes your problem to fix. 117 117
Now in this case, you need to purchase a digital certificate 118 118
from a trusted certificate authority and install it. 119 119
Or you need to renew your expired digital certificate. 120 120
Or you need to install a certificate from a trusted 121 121
certificate authority with a valid route certificate 122 122
on your server. 123 123
In addition to using digital certificates with HTTPS 124 124
websites, 125 125
we also can use digital certificates inside of our networks 126 126
for network authentication using 802.1X with EAP. 127 127
In these cases, your security team's going to run 128 128
your organizations own certificate authority 129 129
to create these digital certificates and issue them 130 130
to the network clients and the servers. 131 131
Again, 132 132
if you're having issues with these digital certificates, 133 133
you need to ensure they're trusted, that they're not expired 134 134
and that they're installed properly on the network devices 135 135
and the network clients. 136 136
Next, we need to talk about licensed feature issues 137 137
that could arise in your networks. 138 138
Sometimes when troubleshooting issues in your network, 139 139
you may come across an error message such as error, 140 140
feature not licensed. 141 141
Now as you can see in this example 142 142
from a NetScaler VPX appliance, 143 143
there are many different features that are enabled 144 144
or disabled based upon the license has been purchased 145 145
by this organization. 146 146
For example, the license they have purchased will allow them 147 147
to do load balancing and content switching. 148 148
But it does not support global server load balancing 149 149
or clustering. 150 150
This is a different feature set that requires a different 151 151
and more expensive license. 152 152
Now if you get an error concerning a particular license 153 153
feature in this or another network device, 154 154
you first need to determine what license 155 155
you have loaded on that device. 156 156
Then compare the license you loaded 157 157
with the features it unlocks. 158 158
If the license is unlocking the features you expected, 159 159
you may need to contact the manufacturer to troubleshoot 160 160
the issue. 161 161
But you may realize you simply purchase the wrong license 162 162
for the features that you need. 163 163
And in this case, 164 164
you need to work with your organization's purchasing agents 165 165
and their contracting professionals to get the right license 166 166
procured so you can load it up into the device. 167 167
Now this is a common issue in large bureaucratic 168 168
organizations where the people who use the things 169 169
and install the devices are not the same ones 170 170
who are empowered to make purchasing decisions. 171 171
As a young network administrator. 172 172
I remember submitting the requisition forms 173 173
to my organization for all the licenses I needed. 174 174
I specified that I needed the platinum license. 175 175
And the contracting person decided, you know what, 176 176
the gold license would be just fine 177 177
because it costs 35% less. 178 178
Well, guess what? 179 179
That contracting person didn't know that a gold license 180 180
didn't include the three critical features 181 181
that we actually needed. 182 182
And those features were the whole reason we were buying 183 183
this particular network appliance. 184 184
So, when we received the license key 185 185
and we tried to load it up on the network appliance, 186 186
we kept getting the feature not licensed error message. 187 187
And it took us almost two days to figure out 188 188
that the reason was our organization gave us a gold license 189 189
and not a platinum license that we really needed. 190 190
So learn from our mistake. 191 191
Make sure you tell the contract personnel 192 192
that substitutions are simply not allowed. 193 193
You need this level of license or just won't work 194 194
for the features you need. 195 195
Next let's discuss BYOD challenges 196 196
or bring your own device challenges. 197 197
Now I don't want to specifically focus on security 198 198
challenges associated with BYOB policies. 199 199
Because we've already talked about that in other videos. 200 200
Instead, I really want to focus on the networking issues 201 201
that you may come across when you're trying to support 202 202
a BYOB policy inside your organization. 203 203
Now BYOD or bring your own device is this policy 204 204
that allows your end users to bring their own smartphones, 205 205
tablets, laptops and other technical devices into work 206 206
and use them on your organization's network. 207 207
Now BYOB allows the organization to save money 208 208
by not having to purchase all these devices 209 209
for the employees. 210 210
But instead they're relying on the employees 211 211
to bring their own equipment and their own devices 212 212
and then do the business on those devices 213 213
using your organization's network. 214 214
Now the biggest challenge with BYOD 215 215
besides securing these devices, 216 216
is actually supporting these devices. 217 217
When a user brings their own device, 218 218
you're no longer supporting one or two models of laptops, 219 219
but instead you've got 50 or 100 220 220
or 200 different varieties now. 221 221
Your employees may bring a Windows 10 Home Edition laptop 222 222
or a MacBook Air or a Chromebook. 223 223
And guess what, 224 224
you're going to be expected to support all of them. 225 225
This is a massive headache and a huge challenge 226 226
for support personnel, 227 227
like our service desk and our network technicians. 228 228
Now, when a device doesn't work properly 229 229
like we want to expect it to, 230 230
we have to determine is it the device 231 231
or is it some software the user loaded 232 232
or is it a network issue that we need to solve? 233 233
This makes it very challenging. 234 234
Honestly, well many organizations think that implementing 235 235
a BYOB policy can save them a lot of money 236 236
because they'll have a reduced capital expenditure 237 237
or CapEx costs. 238 238
It really just increases your OPEX 239 239
or operational expenditures because now you're wasting 240 240
so much time on labor hours to support and troubleshoot 241 241
all these different devices. 242 242
Another challenge with supporting these devices is ensuring 243 243
the security of your network and how these devices 244 244
are going to access your network. 245 245
Are you going to let these devices connect 246 246
on your wired network connections 247 247
or are you going to make them use wireless? 248 248
We require that they be registered ahead of time 249 249
so you know what their MAC addresses are and they can be 250 250
identified in waitlist. 251 251
Or are you going to require these BYOD devices 252 252
to remain on a separate VLAN? 253 253
That way they're not going to touch your internal network 254 254
services, and if they do, 255 255
they have to pass through a screened sub-net. 256 256
All of these are valid questions to consider 257 257
as you determine how you're going to support BYOB 258 258
on your network, 259 259
both operationally and from a troubleshooting 260 260
and repair perspective. 261 261
Finally, let's talk about hardware failures. 262 262
Hardware failures can occur all over your network. 263 263
Your routers, your switches and your firewalls 264 264
can fail for all sorts of reasons 265 265
just like your network clients can. 266 266
As you begin to troubleshoot this issue, 267 267
you need to pinpoint both which device is experiencing 268 268
the failure and which component on the device has failed. 269 269
Once you identify the device that failed, 270 270
such as a router that isn't passing traffic 271 271
from one subnet to another. 272 272
You then need to identify the component that failed. 273 273
Most components on our network devices 274 274
are field replaceable. 275 275
Which means you can swap them out with different components 276 276
and get the device back up and operational very quickly. 277 277
For example, if we had one of our dual power supplies fail 278 278
in a border router, 279 279
we can schedule an emergency maintenance window. 280 280
We can power down the device, open up the chassis, 281 281
replace the broken power supply 282 282
and then return the device to normal operations. 283 283
If an interface card or module is broken or defective, 284 284
we can simply replace that as well. 285 285
And many of these are considered hot pluggable modules. 286 286
So if you have an SFP plus module that fails, 287 287
we can simply replace it without even shutting down 288 288
the network device or taking it offline. 289 289
If a client or server on the other hand 290 290
is found to have a defective component or hardware failure, 291 291
we can work with our CompTIA A+ technicians 292 292
to solve those issues by replacing the associated 293 293
hardware components. 294 294
Normally with a defective or field piece of hardware, 295 295
the fastest way to restore service is simply to replace 296 296
the component that's failed us. 297 297
In some cases, 298 298
such as a failed motherboard on a router or switch, 299 299
you may need to replace the entire device. 300 300
In these cases, you should get a spare switch or router 301 301
from your supply closet, mounted into the rack, 302 302
load up your backup configurations from the failed device 303 303
and put that into the replacement device 304 304
and then reconnect all the cables to it. 305 305
And finally restore service using your new device. 306 306
Then you can take the field device out of the rack, 307 307
return it to the manufacturer for repair 308 308
and then it can become part of your spares in the future 309 309
if it's under warranty or you could dispose of it properly 310 310
if it's reached the end of its useful life.