-: Copper media. 2 2
In this lesson, we're going to talk about copper media. 3 3
Now, when we talk about copper media, 4 4
there are subcategories inside of this larger category 5 5
of copper media, 6 6
and each one is going to have different specifications 7 7
and uses. 8 8
Now in this lesson, 9 9
we're going to talk about three main types of copper media. 10 10
These are coaxial cables, twisted pair cables, 11 11
and serial cables. 12 12
Now, when I talk about copper media, 13 13
the first and oldest one is coaxial cable. 14 14
Also known as co-ax. 15 15
This is going to have an inner insulated conductor 16 16
or center wire that's going to pass all of our data over it. 17 17
This is known as our center core. 18 18
Now we also have this outer shell 19 19
that is a braided metal shield 20 20
to help shield it from any data transmission leakage 21 21
coming from inside the cable outward, 22 22
and it provides protection from the outside in 23 23
against electromagnetic interference 24 24
because of this braided metal shielding. 25 25
Now on the outside, we have this plastic jacket 26 26
and then there's a metallic shield and an insulator 27 27
and inside that insulator, we have that center core 28 28
where all the data's going to pass through. 29 29
Now, where might you find coaxial cables in modern networks? 30 30
Well, there's really two main places. 31 31
First, we're going to have RG-6, 32 32
which is commonly used by your local cable company 33 33
to connect their service to your home. 34 34
It's a very thick version of a coaxial cable. 35 35
Now, once you get inside your home, 36 36
you're going to use what's known as an RG-59, 37 37
and this is going to carry composite video 38 38
between two nearby devices or connect an outlet 39 39
to a cable modem. 40 40
Now, if you have cable TV or satellite TV in your house, 41 41
you're probably using RG-59 cables 42 42
running from the cable or satellite box 43 43
to your TV or to the outlet jack on the wall. 44 44
This is commonly referred to as a coaxial cable or co-ax, 45 45
and it's the most common one you're going to find. 46 46
Now, how does a coaxial cable connect to your device? 47 47
Well, there's two commonly used type of connectors 48 48
when it comes to coaxial cables. 49 49
These are known as an F-type and a BNC connector. 50 50
Now most coaxial cables these days 51 51
are going to have an F-type connector. 52 52
This is basically a screw-on type of connector 53 53
that attaches to the cable box or to the wall jack. 54 54
This is commonly used in cable TV, 55 55
and cable modems for consumer applications. 56 56
Now the second type of connector we have 57 57
is known as a BNC connector, 58 58
also called a Bayonet Neill Concelman connector, 59 59
or a British Naval Connector. 60 60
Now usually network professionals will simply refer 61 61
to all of these as a BNC connector though. 62 62
Now BNC connectors used to be used really heavily 63 63
in networking, 64 64
especially in the early days of computer networks. 65 65
In fact, if you ever come across an old 10BASE-2 66 66
or 10BASE-5 network from the early days of ethernet, 67 67
somewhere around the 1970s or eighties, 68 68
this was the standard connector used by them. 69 69
It was a BNC connector. 70 70
So if all of these things are so old and obsolete, 71 71
why am I even mentioning them? 72 72
Well, because a lot of my students 73 73
will go on to work in jobs for the Department of Defense 74 74
or one of their military subcontractors. 75 75
And they still use a lot of BNC connectors 76 76
as well as RG-6 and RG-59 cabling 77 77
for some of their older network devices, 78 78
because they simply haven't upgraded them yet 79 79
and they still work for some of their older command 80 80
and control systems. 81 81
So you may come across them 82 82
while you're working in the field. 83 83
It's important for you to realize 84 84
what these things look like. 85 85
You have to realize that you don't have to fully screw on 86 86
one of these BNC connectors 87 87
like you would an F-type connector. 88 88
Instead, a BNC connector is going to be used 89 89
by pushing the connector in 90 90
and then twisting it about a half a turn 91 91
to lock it in place. 92 92
Now, there is a newer style coaxial cable 93 93
that is being used in modern applications as well. 94 94
This one is known as twinaxial. 95 95
Now a twinaxial cable is similar to a coaxial cable, 96 96
but instead of having just one conductor, 97 97
there's going to be two inner conductors to carry the data. 98 98
Twinaxial cables are used for very short range, 99 99
high speed connections between devices. 100 100
For example, there's a use case for using an SFP plus 101 101
direct attached copper cable between two different switches 102 102
that are shorter than about seven meters apart. 103 103
Now, if you decide to use twinaxial cable for this, 104 104
you can avoid using fiber cables 105 105
and it'll save you a bit of money 106 106
if your networking devices 107 107
will support this type of connection. 108 108
In this application, you're going to be able to get speeds 109 109
of up to 10 gigabits per second, 110 110
over that twinaxial cable. 111 111
And it uses a lot less energy than traditional copper cables 112 112
to achieve this level of speed. 113 113
That said, personally, 114 114
I've never had to use twinaxial cables in my life. 115 115
And instead I've either relied on the twisted pair cable 116 116
or a fiber optic cable between my switches 117 117
for my high-speed trunks. 118 118
Now the second type of copper cable you may run into 119 119
is known as a serial cable. 120 120
These cables usually have a series of straight copper wires 121 121
inside a single cable or plastic jacket. 122 122
Normally they're going to be terminated with a DB-9 123 123
or DB-25 connector, 124 124
which is a D shaped subminiature connector 125 125
with nine or twenty-five pins at the end of it. 126 126
These cables are also known as an RS-232 cable, 127 127
since that's the signaling method that's used 128 128
when transmitting data over these cables. 129 129
These cables are very old and they're not commonly used 130 130
in modern networks, but you may come across one 131 131
if you're working with an older network connectivity method, 132 132
such as an external ISDN modem 133 133
or a T1 or an E1 modem connection. 134 134
Our third type of copper cable we have 135 135
is known as twisted pair cable. 136 136
Now twisted pair is going to be the most popular 137 137
local area network cabling technology 138 138
that we're going to use in our networks today. 139 139
If you're plugging in a network cable to your laptop 140 140
or your desktop, 141 141
you're usually doing this using a copper twisted pair cable. 142 142
Inside this cable, 143 143
there are eight individually insulated wires 144 144
that are going to be inside of this cable sheath. 145 145
And each of those is twisted up into a pair, 146 146
which is why we call it twisted pair cable. 147 147
Now, if you open up this cable, 148 148
you can see there are going to be four pairs, 149 149
each twisted with two wires in each of those pairs. 150 150
Now the twist here is really important. 151 151
The more twists you have within an inch of the cable 152 152
the better the protection that cable has 153 153
from electromagnetic interference or EMI. 154 154
If you have less twists 155 155
and the cable becomes more susceptible 156 156
to more electromagnetic interference, 157 157
and this will also mean you have slower speeds 158 158
for your cable. 159 159
This becomes really important 160 160
because the more interference you have, 161 161
the worse your data transmission rate is going to be 162 162
because you have to retransmit your data more often. 163 163
This is going to slow down your overall throughput 164 164
and bandwidth in your network. 165 165
As we go through this lesson, 166 166
we're going to start to discuss the different categories 167 167
of cable, going from CAT 5 up to CAT 8. 168 168
And the common theme here 169 169
is that the higher the category number, 170 170
the more twist you're going to find per inch of cable, 171 171
and therefore the higher speed 172 172
that particular cable category 173 173
is going to be able to achieve. 174 174
Now, when we're dealing with the twisted pair cabling, 175 175
you're going to hear it broken down into one of two types, 176 176
either UTP or STP. 177 177
UTP stands for unshielded twisted pair 178 178
and STP stands for shielded twisted pair. 179 179
On this screen, 180 180
you can see an example of an unshielded twisted pair cable. 181 181
Now notice the wires are twisted and they're covered 182 182
in this plastic jacket on the outside 183 183
that's going to protect it from the elements. 184 184
Now with UTP, you're going to find a much cheaper cable. 185 185
When you start using STP, 186 186
it's going to be a little bit harder to use, 187 187
and it's going to cost a little bit more. 188 188
When you're dealing with UTP, 189 189
there is no metal being used in the part of the shielding 190 190
and therefore UTP is going to be cheaper 191 191
because it's all plastic, 192 192
except for those thin copper wires inside of our four pairs 193 193
making up those eight wires. 194 194
Now, because of it's low cost, and it's easy to use, 195 195
unshielded twisted pair cabling is the media of choice 196 196
for most local area networks these days. 197 197
UTP can be bent very easily 198 198
as you're pushing it through conduit, 199 199
throughout your ceilings and your walls 200 200
and you can install it with very low cost tools 201 201
in just a few days of training in most cases. 202 202
The second type of twisted pair cable is known as STP 203 203
or shielded twisted pair. 204 204
Now STP is just like UTP, 205 205
except each twisted pair inside that cable sheath 206 206
is going to be wrapped with some metal foil. 207 207
And there's also going to be this 208 208
braided metallic shield wrapping 209 209
around all four of those pairs. 210 210
This means the wires in an STP cable 211 211
are going to be twisted up in pairs just like they were in UTP. 212 212
But the difference is, they have this metal shielding 213 213
that else minimize EMI between the inner twisted pairs 214 214
even more. 215 215
And there's also this outer braiding shield 216 216
to minimize EMI from the outside environment too. 217 217
Essentially we're taking the best things from UTP 218 218
and all that shielding from using a coaxial cable 219 219
and putting it into one device. 220 220
Now, because of all this extra metal though, 221 221
this is going to make shielded twisted pairs cost more 222 222
than an equivalent category of unshielded twisted pair. 223 223
Other than that, STP and UTP operate about the same 224 224
with the exception of the EMI interference 225 225
that's going to be less with STP. 226 226
Now, both STP and UTP 227 227
both have the same amount of distance limitations. 228 228
Either of them can go about a hundred meters, 229 229
which is around 300 feet. 230 230
Both also use the same type of connectors to terminate them. 231 231
And the wires on the inside are exactly the same 232 232
with the exception of that metal shielding 233 233
being wrapped around them in the case of STP. 234 234
Now, speaking of connectors, 235 235
let's talk about the two connector types 236 236
that's used with twisted pair cabling. 237 237
These are RJ45 and RJ11. 238 238
Now, RJ45 is the most commonly used connector 239 239
in our networks. 240 240
The RJ45 connector is a plastic eight pin connector, 241 241
and it looks like a fatter version 242 242
of a traditional landline phone jack. 243 243
Now, RJ45 is used all the time in ethernet based networks, 244 244
including ones with CAT 5, CAT 6, CAT 7, 245 245
or CAT 8 cables. 246 246
If you're using an RJ45 connector with a CAT 5 cable, 247 247
it's only going to have to use four of the eight pins. 248 248
The other four are reserved for future use, 249 249
but they can be used for other applications, 250 250
such as power over ethernet and things like that. 251 251
Ever since we moved to gigabit ethernet 252 252
with 1000BASE-T and higher 253 253
all four pairs and their eight pins 254 254
are going to be used for data transfer. 255 255
We're going to talk more about the different categories 256 256
and speeds in just a moment. 257 257
The second type of connector that we use 258 258
with twisted pair cables is known as RJ11. 259 259
Now, RJ11 is a six pin connector. 260 260
And when used in an RJ11 configuration, 261 261
only two of those pins are actually going to be used. 262 262
Commonly, you're going to find this in phone systems 263 263
to connect your phone to a landline jack. 264 264
Now, one of these pins is going to be reserved for the ring, 265 265
and one is going to be reserved for the signal 266 266
inside of these phone systems. 267 267
If you're using a DSL modem for your internet connectivity, 268 268
or you're providing VoIP services 269 269
through an analog telephone adapter, 270 270
you may come across an RJ11. 271 271
But otherwise they're not very common 272 272
inside our local area networks. 273 273
When creating one of these phone lines, 274 274
you can simply use CAT 5 or similar cabling, 275 275
and then put an RJ11 connector on the end 276 276
instead of an RJ45. 277 277
Now, as I said, in most networks, 278 278
you're going to be using an RJ45 connector 279 279
at the end of an unshielded twisted pair cable, 280 280
because these are the most common thing 281 281
you're going to run across in the field. 282 282
Now you may be wondering, I keep saying, RJ. 283 283
What does RJ stand for? 284 284
Like RJ45 and RJ11? 285 285
Well, it stands for Registered Jack. 286 286
Basically, they are the standardized 287 287
telecommunication network interfaces 288 288
that are used to carry voice or data, 289 289
and they specify the standards that the device needs to meet 290 290
in order to connect to the phone or data network. 291 291
There are lots of different variants out there, 292 292
but RJ11 is used for phone networks 293 293
and RJ45 is used for data networks 294 294
as the two most popular ones out there. 295 295
And these are the only two you need to know for the exam. 296 296
All right, let's talk about bandwidth and throughput. 297 297
Bandwidth is your theoretical measure of how much data 298 298
could be transferred from a source to its destination. 299 299
Throughput on the other hand is the actual measure 300 300
of how much data is successfully transferred 301 301
from a source to its destination. 302 302
Now notice these terms are very closely related 303 303
and you'll often hear people use them interchangeably 304 304
when you're working in the field. 305 305
But technically there is a subtle difference here. 306 306
As we talk about the different cables and categories, 307 307
we're going to be talking about them in terms of bandwidth, 308 308
which is their theoretical measure 309 309
of how much data could be transferred 310 310
from the source to a destination, 311 311
as opposed to what you may see in your own networks 312 312
under real world conditions. 313 313
That real-world conditions and the things you're seeing, 314 314
that is throughput. 315 315
All right, for the exam, 316 316
you need to know several different categories 317 317
of twisted pair of cabling, specifically CAT 3, 318 318
CAT 5, CAT 5e, CAT 6, CAT 6a, 319 319
CAT 7 and CAT 8. 320 320
For each cable type, you need to know its category number, 321 321
it's ethernet standard, 322 322
the bandwidth or transmission speed it uses 323 323
and the maximum distance it can operate. 324 324
Now, when I mentioned an ethernet standard, 325 325
this is going to be a designation 326 326
given to a particular category 327 327
and allows us to really easily understand 328 328
the bandwidth and the cable type that's going to be used. 329 329
For example, just looking at that standard number, 330 330
you can tell if it's copper or fiber. 331 331
So let's start out with CAT 3. 332 332
First, we have 10BASE-T, 333 333
which is our first ethernet cable type 334 334
that operated over twisted pair cabling 335 335
and it was starting to be used all the way back in the 1980s 336 336
and became popular throughout the eighties and nineties. 337 337
The maximum speed of a CAT 3 cable, 338 338
which is known as a 10BASE-T is 10 megabits per second. 339 339
Now like most twisted pair cables, 340 340
CAT 3 can only go up to a hundred meters 341 341
or around 300 feet in distance. 342 342
Now notice the standard here is written as a number, 343 343
the word base, and then a letter, in this case T. 344 344
This makes designation of it very quick and easy 345 345
so you can see the speed, 10 megabits per second, 346 346
and the cable type being used. 347 347
T for twisted pair. 348 348
For all the twisted pair cables, 349 349
you're going to see there are base-T or base-TX. 350 350
When we get to the fiber cables later on, 351 351
we're going to see that they're going to use that base notation, 352 352
but they'll have different letters at the end. 353 353
And those letters are going to change 354 354
based upon the type of fiber being used, 355 355
whether it's a single mode or multimode fiber. 356 356
So when we talk about a CAT 3 or 10BASE-T network, 357 357
remember this was originally the ethernet network, 358 358
and it is the slowest one we're going to cover. 359 359
Next, we have CAT 5 with 100BASE-TX, 360 360
which was called fast ethernet. 361 361
Now fast ethernet operates at a hundred megabits 362 362
per second, 363 363
which is why it is called 100BASE-TX network. 364 364
Now the TX here stands for twisted pair, fast ethernet, 365 365
and is the only twisted pair network, 366 366
that uses something other than a T in the base notation. 367 367
Again, just like CAT 3 cables, 368 368
CAT 5 cables, or 100BASE-TX cables 369 369
can only go up to a hundred meters in length 370 370
before their signal must be repeated using a switch, 371 371
a router or some kind of a repeater device. 372 372
Next, we have CAT 5e, which is known as 1000BASE-T. 373 373
Now a 1000BASE-T network or gigabit ethernet 374 374
is going to operate at 1000 megabits per second, 375 375
which is also known as one gigabit per second. 376 376
Again, our distance here is limited to only 100 meters. 377 377
Next we have CAT 6 which can operate either 1000BASE-T 378 378
or 10GBASE-T. 379 379
Now, if CAT 6 is going to be used with a 1000BASE-T network, 380 380
it can operate at 1000 megabits per second 381 381
or one gigabit per second, just like CAT 5e did, 382 382
and it goes up to 100 meters in length. 383 383
Now CAT 6 can also go faster 384 384
and it can go up to 10 gigabits per second, 385 385
using a 10GBASE-T network. 386 386
But when you use this higher speed, 387 387
you can only go 55 meters instead of the full 100 meters. 388 388
Next, we have CAT 6a 389 389
which was an improvement over CAT 6. 390 390
CAT 6a will allow you to operate 10GBASE-T networks 391 391
at that full 10 gigabits per second, 392 392
all the way up to a hundred meters. 393 393
Next we have CAT 7, 394 394
and CAT 7 is going to operate 10GBASE-T as well, 395 395
giving you that full 10 gigabits per second 396 396
at up to a hundred meters. 397 397
Oddly enough, CAT 7 was actually released over six years 398 398
before CAT 6a was, 399 399
but it could use either a traditional RJ45 style connector 400 400
or a different connector known as TERA, 401 401
T-E-R-A, 402 402
and therefore it was able to reach 10 gigabit speeds, 403 403
much faster over the hundred meters 404 404
before CAT 6 could be modified 405 405
into the newer CAT 6a standard. 406 406
All that said, for the exam, 407 407
I just need you to remember that both CAT 6a 408 408
and CAT 7 are both considered 10GBASE-T networks 409 409
and can operate up to a maximum of 100 meters 410 410
at a speed of 10 gigabits per second. 411 411
Finally, we have CAT 8 412 412
which can operate 40GBASE-T networks, 413 413
which is able to provide 40 gigabits per second, 414 414
but only up to 30 meters. 415 415
All right, let's summarize with a chart 416 416
and see if we can find the easy way 417 417
to memorize all of these different facts and figures. 418 418
Starting with CAT 3 and going up to CAT 7, 419 419
we can just start multiplying by 10 each time 420 420
to get our bandwidth and our ethernet standards. 421 421
So we go from 10 megabits per second 422 422
to a hundred megabits per second, 423 423
to a thousand megabits per second 424 424
to 10 gigabits per second. 425 425
for CAT 8, you just have to remember 426 426
that it switches by multiplier of four, 427 427
getting us up to 40 gigabits per second. 428 428
Now for the distance, this is also pretty easy 429 429
because it's almost always going to be 100 meters. 430 430
Now, there are only two exceptions. 431 431
So if you can remember the exceptions 432 432
are CAT 6 at 55 meters and CAT 8 at 30 meters. 433 433
Then you just need to remember 434 434
the rest are all going to be 100 meters. 435 435
Now let's talk about length for just a minute here, 436 436
because you're going to get questions on the exam 437 437
where the answer comes down 438 438
to how long the cable is going to be. 439 439
Now they will usually come straight out 440 440
and ask you a question like 441 441
what's the maximum length of a CAT 5e cable. 442 442
That would be way too easy. 443 443
So instead, they're usually going to incorporate 444 444
it into some kind of troubleshooting question. 445 445
For example, you might get something that looks like this. 446 446
You working as a network technician 447 447
and a user in the corner office 448 448
is complaining that they're having intermittent 449 449
network connectivity issues when using a CAT 5e cable 450 450
and connect it to the LAN. 451 451
Their office is 85 meters 452 452
from the closest intermediate distribution frame. 453 453
Which of the following might be the source 454 454
of their connectivity issues? 455 455
Then you might get some options like, 456 456
the connection is set to half-duplex 457 457
instead of full duplex, 458 458
or the connection may have exceeded the maximum distance 459 459
for a CAT 5e cable, 460 460
or the connection is using WPA instead of WPA2, 461 461
or the connection needs to be set to encrypted 462 462
instead of un-encrypted. 463 463
The answer here would be that the connection 464 464
may have exceeded the maximum distance for a CAT 5e cable. 465 465
But wait a minute, Jason, 466 466
didn't you just say the maximum cable length 467 467
was a hundred meters 468 468
and this question said we were only 85 meters away. 469 469
What the heck is going on here? 470 470
Well, yes, the maximum cable length is a hundred meters, 471 471
but that's often the maximum, not the minimum. 472 472
Oftentimes in the real world, 473 473
you're going to see that you can't get 474 474
a full a hundred meters in cable length 475 475
from these types of cables 476 476
because there's interference from fluorescent lights 477 477
and other sources of EMI. 478 478
Also, the question said that the IDF was 85 meters away. 479 479
Not that the cable length was 85 meters. 480 480
So if the IDF is 85 meters away, 481 481
you're still going to have to run that cable 482 482
from the patch panel up from the IDF into the ceiling, 483 483
and then from the ceiling over to the office 484 484
and from the office ceiling down to the wall drop 485 485
and then from the wall drop, 486 486
you have a patch cable connecting to the computer. 487 487
All of this is going to add length 488 488
because going up and down to the ceiling 489 489
might be another four or five meters. 490 490
You might also have to go from that patch cable 491 491
might be a 15 or 20 meter cable 492 492
going from one side of the office to the other. 493 493
You can't just assume that there's a straight line 494 494
from the IDF to the corner office, 495 495
because it might not be true. 496 496
For this reason, I usually recommend keeping your cable runs 497 497
under 70 meters in length 498 498
when you're going from the IDF to the office 499 499
that you want to run the jack to. 500 500
This allows for the ups, downs, overs and arounds 501 501
that you're going to actually have to do 502 502
when you're running that cable. 503 503
Now, would I expect you to get this question right 504 504
if I asked it to you right now? 505 505
Well, no, because we haven't even covered 506 506
all the things covered in this question, 507 507
like the intermediate distribution frame, patch panels, 508 508
and other key components. 509 509
But I wanted to give you an idea of how these questions 510 510
are going to be worded and work together to combine concepts 511 511
across different domains, into a single question. 512 512
This question, for example, 513 513
covered concepts from three different objectives, 514 514
across three different domains. 515 515
All right, 516 516
so now that we've talked about the different cable types, 517 517
their categories and the connections, 518 518
we need to talk about how to actually wire these cables 519 519
into the connectors to allow us to connect these things 520 520
to our devices, using the right pinouts. 521 521
On the exam, it would be completely fair of them 522 522
to ask you to create a straight-through cable 523 523
or a crossover cable, because one of the exam objectives 524 524
states that you should be able to troubleshoot 525 525
common cable connectivity issues 526 526
using the appropriate tools, such as a cable stripper, 527 527
cable crimper, and cable tester. 528 528
So to ensure you're ready for that, 529 529
we need to talk a bit more about the way the ends are wired 530 530
and the proper sequence for the pinouts 531 531
of these connectors. 532 532
Now I just mentioned a term that you should be familiar with 533 533
from backing your A-plus studies. 534 534
But like I promised before, 535 535
I'm going to do a quick refresher of this term 536 536
to make sure everybody's on the same page. 537 537
Now that term is a straight-through cable. 538 538
A straight-through cable is also known as a patch cable. 539 539
This type of cable contains the exact same pinouts 540 540
on both ends of the cable. 541 541
This is why it's known as a straight-through, 542 542
because pin one on one side goes straight on through 543 543
to pin one on the other side of the cable. 544 544
Now, to keep everyone consistent when we make cables, 545 545
you're going to find there's a standard pinout 546 546
known as a 568A and a 568B standard. 547 547
Now 568B is the standard that's preferred 548 548
for wiring jacks inside your buildings. 549 549
And most people are going to use a 568B 550 550
to 568B wiring scheme for straight-through patch cables. 551 551
Now, what does that look like? 552 552
Well, if we count our pins from one to eight, 553 553
we're going to have a color scheme of orange white, orange, 554 554
green white, blue, blue white, green, brown white, brown. 555 555
That is going from pins one to eight. 556 556
So both sides of our cable will match up 557 557
and this will create a straight-through patch cable. 558 558
These patch cables are used to connect a DTE to a DCE. 559 559
Now, what is a DTE and a DCE? 560 560
Well, a DTE is a data terminal equipment, 561 561
which includes things like laptops and desktops, servers, 562 562
and routers. 563 563
These are all considered end point devices 564 564
that connect to a piece of data communications equipment 565 565
or DCE. 566 566
Now a DCE is things like a switch, a modem, a hub, 567 567
or a bridge. 568 568
If you're connecting a DTE to a DCE, 569 569
or a DCE to a DTE, you can use a straight-through cable. 570 570
Basically any terminal device can connect 571 571
to any communication device using one of these patch cables. 572 572
But if I wanted to connect a switch to another switch, 573 573
since they're both data communication equipment, 574 574
I have to use a different type of cable 575 575
known as a crossover cable. 576 576
Anytime you connect a DTE to a DTE, 577 577
a terminal to a terminal 578 578
or a DCE to a DCE, 579 579
communication equipment to communication equipment, 580 580
you have to use a crossover cable. 581 581
So if I connect a computer to a laptop, 582 582
that's going to need a crossover cable. 583 583
If I'm connecting a computer to a switch, I don't need one. 584 584
I can use a patch cable. 585 585
So, what makes a crossover cable so special? 586 586
Well across over cable 587 587
is going to take your send and receive pins 588 588
from that cable and swap those on the other end 589 589
when you create your connector and you pin it out. 590 590
So on one end, you're going to need to have a 568B, 591 591
and on the other end, you're going to have a 568A. 592 592
This is used to connect a workstation to a workstation 593 593
or a switch to a switch. 594 594
Now in general, you should always use a crossover cable 595 595
when you're going from a switch to a switch. 596 596
For the exam, I want you to remember 597 597
that a switch to a switch requires a crossover cable. 598 598
The reason I'm making a big deal about this 599 599
is that in the real world, this isn't always the case. 600 600
Now this is because most modern switches 601 601
have something known as MDIX, 602 602
which stands for medium dependent interface crossover. 603 603
Essentially MDIX is an automated way 604 604
to electronically simulate using a crossover cable 605 605
even if you're using a straight-through patch cable. 606 606
Essentially your modern switch, if it supports MDIX 607 607
will allow you to use a patch or straight-through cable, 608 608
and it will switch the pinout electronically inside itself 609 609
to make it work. 610 610
But for the exam, you should always assume a switch 611 611
is going to be an older device that does not support MDIX, 612 612
unless the question specifically states 613 613
that the switch is using MDIX. 614 614
Now we'll talk about this more when we go to troubleshooting 615 615
way in the end of this course, but for right now, 616 616
I wanted to bring this up 617 617
because it's something that is going to come back and bite you 618 618
if you don't remember it. 619 619
Remember when there are two switches 620 620
and they're not communicating 621 621
it's usually because somebody is putting a patch cable there 622 622
or a straight-through cable there 623 623
instead of doing a crossover cable 624 624
and that switch doesn't support MDIX. 625 625
If your switch doesn't support MDIX, 626 626
you have to use a crossover cable 627 627
to make those devices talk. 628 628
All right, let's look at the pinout a little bit closer, 629 629
and this time let's look at our 568A 630 630
and 568B wiring standards. 631 631
Remember, 568B is the standard we use 632 632
for all our interior wiring 633 633
and for both ends of a straight-through cable or wall jack. 634 634
But if we want to do a crossover cable, 635 635
we're going to use 568B on one end 636 636
and 568A on the other end. 637 637
When you do this, you're going to start with 568B on one end, 638 638
and then switch out pins one, two, three, and six 639 639
on the other end, 640 640
so that we have our transmit and receive pins 641 641
in a different place when we create that crossover cable. 642 642
Essentially your orange and your green pairs 643 643
are going to swap places. 644 644
Now, do you have to memorize this? 645 645
Yes, unfortunately you do. 646 646
In the real world, you really don't have to even memorize 647 647
because you can carry your smartphone with you 648 648
or a small chart in your pocket. 649 649
And whenever you're going to make a cable, 650 650
you could pull it out of your wallet and look at it. 651 651
But for the exam, you need to know this pattern. 652 652
As I said before, they may give you a question that says, 653 653
wire up the correct pinout for a 568B connector. 654 654
Then you're going to have to drag and drop 655 655
the color of the wire to the right pin 656 656
as part of a simulation. 657 657
Or they can be really mean 658 658
and just ask you to create a patch cable, 659 659
or a crossover cable. 660 660
And you're going to have to drag and drop the right wires 661 661
into the right spots in an RJ45 connector 662 662
from pins one to eight, for both sides. 663 663
If that happens, you are really going to hope 664 664
you have memorized the color schemes 665 665
for both 568B and 568A, right? 666 666
Now, the last thing we need to talk about 667 667
in terms of copper cabling 668 668
is the concept of plenum versus non plenum. 669 669
So, what does plenum mean? 670 670
Well, plenum cable is a special coating 671 671
that's put on an unshielded or shielded twisted pair cable, 672 672
and it provides a fire-retardant chemical layer 673 673
to the outer insulating jacket of that cable. 674 674
Now, if you have a plenum rated cable, 675 675
this means it's more fire resistant, 676 676
and it also minimizes the amount of dangerous fumes 677 677
that are released if the cable catches on fire. 678 678
If you're going to be running cables in a place 679 679
that you physically can't see such as the ceiling, 680 680
the walls, a raised floor, or near air ducts, 681 681
you must use plenum cable per the laws 682 682
and county requirements in your state 683 683
or in the county in which you live. 684 684
Now, plenum cable is a bit more expensive 685 685
than non plenum cable, 686 686
but it is a major safety issue to not use plenum cable. 687 687
So you simply have to use plenum cable 688 688
anytime you're going to put a cable in a place 689 689
that your users can't visibly see. 690 690
Now, on the other hand, 691 691
if you're running a cable from a wall jack 692 692
to the back of your desktop or laptop, 693 693
you don't need to spend the extra money on plenum cable. 694 694
For these connectors, 695 695
it's okay to save a little bit of money 696 696
by using these non plenum rated cables. 697 697
Non plenum rated cables are also known as PVC, 698 698
and they can either be shielded 699 699
or unshielded twisted pair cables. 700 700
Now on the exam, remember, 701 701
plenum is for anything you cannot see, 702 702
but again, you cannot put non plenum cables 703 703
in your ceilings, walls, raised floors or air ducks. 704 704
This is a big, big no-no, 705 705
and it's a very dangerous thing 706 706
for the safety of your networks and your people.