1
00:00:02,712 --> 00:00:05,212
(light music)

2
00:00:09,081 --> 00:00:12,973
- Within the ICND1 blueprint
under the general bullet point

3
00:00:12,973 --> 00:00:14,513
of network fundamentals,

4
00:00:14,513 --> 00:00:17,385
they include a section on
IPv6, this is the place

5
00:00:17,385 --> 00:00:21,025
where they first want to
introduce you to IPv6.

6
00:00:21,025 --> 00:00:23,058
So these next several videos
are going to be little snippets

7
00:00:23,058 --> 00:00:26,561
of me talking about
various aspects of IPv6.

8
00:00:26,561 --> 00:00:29,669
We're not actually gonna get
into the configuration of IPv6.

9
00:00:29,669 --> 00:00:32,496
First of all, I have to go
through basic iOS command lines

10
00:00:32,496 --> 00:00:34,289
before we even think about that.

11
00:00:34,289 --> 00:00:36,081
But I just wanna introduce IPv6

12
00:00:36,081 --> 00:00:37,900
from a theoretical perspective.

13
00:00:37,900 --> 00:00:41,765
So this is the first video in
that series introducing IPv6.

14
00:00:41,765 --> 00:00:45,936
So let's first talk a little
bit about the history of IPv6.

15
00:00:45,936 --> 00:00:49,717
We know that IPv4 was
actually first developed

16
00:00:49,717 --> 00:00:51,884
back with RFC 791 in 1981,

17
00:00:55,183 --> 00:00:57,150
I think it was 1981 or 1982

18
00:00:57,150 --> 00:00:59,567
when IPv4 was just developed.

19
00:01:00,678 --> 00:01:04,514
And initially, at the very,
very beginning stages,

20
00:01:04,514 --> 00:01:08,070
it was only developed for like
institutions like colleges

21
00:01:08,070 --> 00:01:10,534
and universities that were experimenting

22
00:01:10,534 --> 00:01:11,367
with IPv4.

23
00:01:12,270 --> 00:01:16,722
This idea of an internet was
not even envisioned back then.

24
00:01:16,722 --> 00:01:19,634
But as more and more
people started connecting

25
00:01:19,634 --> 00:01:22,266
to the IPv4 backbone and using it,

26
00:01:22,266 --> 00:01:25,234
and it began expanding from just research

27
00:01:25,234 --> 00:01:28,118
to communications, and gaming,

28
00:01:28,118 --> 00:01:31,114
this idea of IPv4 addresses became more

29
00:01:31,114 --> 00:01:33,914
and more and more popular.

30
00:01:33,914 --> 00:01:37,497
So, by 1992 there was
an impending shortage

31
00:01:39,350 --> 00:01:42,234
of IPv4 address space the recogni--

32
00:01:42,234 --> 00:01:44,670
like I should say that in
1992 they recognized that,

33
00:01:44,670 --> 00:01:47,078
"Uh oh, the way things are going,

34
00:01:47,078 --> 00:01:50,970
"with how quickly the IPv4
addresses are starting

35
00:01:50,970 --> 00:01:54,470
"to be consumed, we
recognize that at some point

36
00:01:54,470 --> 00:01:56,234
"there's gonna be a shortage."

37
00:01:56,234 --> 00:01:58,978
Now there was not a shortage back in 1992,

38
00:01:58,978 --> 00:02:00,518
but that's when they first recognized

39
00:02:00,518 --> 00:02:02,562
this is gonna be a problem.

40
00:02:02,562 --> 00:02:04,074
At some point in the future,

41
00:02:04,074 --> 00:02:06,174
if things keep going
the way they're going,

42
00:02:06,174 --> 00:02:09,507
we are going to run out of IPv4 subnets.

43
00:02:10,402 --> 00:02:11,746
Now what does that actually mean?

44
00:02:11,746 --> 00:02:13,818
Well, that means that
whenever that point is,

45
00:02:13,818 --> 00:02:16,226
if somebody develops a new company

46
00:02:16,226 --> 00:02:18,662
and they want to connect to the internet,

47
00:02:18,662 --> 00:02:21,210
we're not gonna have a
subnet to give to them.

48
00:02:21,210 --> 00:02:23,385
We're not gonna, if
there's an existing company

49
00:02:23,385 --> 00:02:26,123
that expands and they add a new campus,

50
00:02:26,123 --> 00:02:28,167
we're not gonna have any
addresses that we can give to them

51
00:02:28,167 --> 00:02:30,659
'cause they will all be gone.

52
00:02:30,659 --> 00:02:32,703
So they recognized back in 1992

53
00:02:32,703 --> 00:02:35,286
that this was an inevitability.

54
00:02:36,735 --> 00:02:38,499
So two years later,

55
00:02:38,499 --> 00:02:41,243
the internet engineering task
force launched their work

56
00:02:41,243 --> 00:02:43,826
into a new version of IP, IPv6.

57
00:02:46,823 --> 00:02:50,323
So IPv6, the initial motivator for it was,

58
00:02:51,407 --> 00:02:54,459
"Let's restructure the address,

59
00:02:54,459 --> 00:02:56,290
"let's make the address bigger."

60
00:02:56,290 --> 00:03:00,070
you know, with 32-bits, there's
billions of combinations

61
00:03:00,070 --> 00:03:03,754
of addresses with 32-bits
with an IPv4 address.

62
00:03:03,754 --> 00:03:06,358
And you might think, "Wow,
with that many combinations,

63
00:03:06,358 --> 00:03:08,122
"how could we ever run out?"

64
00:03:08,122 --> 00:03:10,994
Well, here we are in 2016,
and we actually are starting

65
00:03:10,994 --> 00:03:13,598
to run out in certain parts of the world,

66
00:03:13,598 --> 00:03:15,530
even with billions of addresses.

67
00:03:15,530 --> 00:03:17,994
So, the IETF decided,

68
00:03:17,994 --> 00:03:22,161
"Let's redo the Internet
Protocol, version six of it,

69
00:03:23,006 --> 00:03:26,226
"and let's make the
address space much bigger

70
00:03:26,226 --> 00:03:29,978
"so that it'll hopefully
never run out of addresses."

71
00:03:29,978 --> 00:03:33,590
So that was the initial
motivator of revising IP.

72
00:03:33,590 --> 00:03:34,922
But then while they were at it,

73
00:03:34,922 --> 00:03:36,714
they thought, "You know what?

74
00:03:36,714 --> 00:03:40,522
"Since we're redoing IP, why
don't we take this opportunity

75
00:03:40,522 --> 00:03:43,126
"because who knows when we'll
have this opportunity again,

76
00:03:43,126 --> 00:03:44,946
"to change some other things

77
00:03:44,946 --> 00:03:47,006
"about the Internet Protocol as well;

78
00:03:47,006 --> 00:03:48,966
"not just making the address space bigger,

79
00:03:48,966 --> 00:03:50,646
"but changing some other things as well."

80
00:03:50,646 --> 00:03:52,438
And in another video coming up,

81
00:03:52,438 --> 00:03:55,546
I'll show you the differences
between the IPv4 header,

82
00:03:55,546 --> 00:03:59,713
that we've looked at
already, and the IPv6 header.

83
00:04:00,614 --> 00:04:02,364
So in 1998, RFC 2460,

84
00:04:04,814 --> 00:04:08,981
which was the first RFC
document for IPv6, was written.

85
00:04:10,318 --> 00:04:12,306
Now let's put things in
perspective here a little bit.

86
00:04:12,306 --> 00:04:13,846
Remember I told you that

87
00:04:13,846 --> 00:04:17,096
when IP first came out in 1981 or 1982,

88
00:04:18,802 --> 00:04:20,930
there was no such thing as subnet mask,

89
00:04:20,930 --> 00:04:24,542
it was purely class A,
class B, and class C.

90
00:04:24,542 --> 00:04:28,910
So the idea of a subnet mask
actually came out in 1985.

91
00:04:28,910 --> 00:04:31,010
So that was RFC 950.

92
00:04:31,010 --> 00:04:33,110
No one's ever gonna expect
you to memorize this stuff,

93
00:04:33,110 --> 00:04:36,890
none of these dates are
gonna be on the ICND1 exam,

94
00:04:36,890 --> 00:04:39,606
I just wanna sort of prep you
and get your mind thinking

95
00:04:39,606 --> 00:04:41,818
about why did they create
this thing in the first place?

96
00:04:41,818 --> 00:04:44,954
What problem was it designed to solve?

97
00:04:44,954 --> 00:04:48,787
So, IP 1991: subnet masks
added to IP in 1985,

98
00:04:50,890 --> 00:04:53,354
and then seven years
later they recognized,

99
00:04:53,354 --> 00:04:55,146
"Uh oh, we can see a future

100
00:04:55,146 --> 00:04:57,358
"where things are gonna
start running out."

101
00:04:57,358 --> 00:05:01,525
SO, in 1998, they wrote the
actual first document for IPv6.

102
00:05:03,157 --> 00:05:06,240
Then in 2006, so it took eight years,

103
00:05:07,130 --> 00:05:09,482
you can see this from '98 to 2006,

104
00:05:09,482 --> 00:05:13,474
it took eight years for
IPv6 address spacing

105
00:05:13,474 --> 00:05:15,686
to really stabilize.

106
00:05:15,686 --> 00:05:17,786
In other words, there was a
lot of back and forth about,

107
00:05:17,786 --> 00:05:19,214
"Well, addresses should look like this."

108
00:05:19,214 --> 00:05:20,726
"Well, these addresses should be used."

109
00:05:20,726 --> 00:05:22,350
"No, these addresses
should be kept private."

110
00:05:22,350 --> 00:05:24,590
"No, we should keep these
addresses in reserve."

111
00:05:24,590 --> 00:05:25,423
"Oh no, we should look

112
00:05:25,423 --> 00:05:26,694
"at the bits a little bit differently."

113
00:05:26,694 --> 00:05:28,682
So it took eight years for them

114
00:05:28,682 --> 00:05:31,174
to finally settle down and stabilize

115
00:05:31,174 --> 00:05:34,786
on what the IPv6 address
structure would actually look like

116
00:05:34,786 --> 00:05:36,410
and how it would be used.

117
00:05:36,410 --> 00:05:38,243
And that was RFC 4291.

118
00:05:40,358 --> 00:05:44,525
Back in 2008, so now we're
talking about eight years ago,

119
00:05:45,538 --> 00:05:47,638
before this recording was made,

120
00:05:47,638 --> 00:05:50,046
the United States Federal
Government mandated

121
00:05:50,046 --> 00:05:54,106
that all backbone devices
running on Federal Agencies,

122
00:05:54,106 --> 00:05:57,438
so for example, all the routers
and devices that were owned

123
00:05:57,438 --> 00:06:01,246
by the CIA, the FBI, the
Social Security Administration,

124
00:06:01,246 --> 00:06:04,634
all federal government agencies,
their backbone routers,

125
00:06:04,634 --> 00:06:06,678
and what do we mean by backbone router?

126
00:06:06,678 --> 00:06:08,806
'Cause I know I haven't
talked about that term yet.

127
00:06:08,806 --> 00:06:13,342
So, in the structure of a
network, we've talked about,

128
00:06:13,342 --> 00:06:16,002
I did talk about earlier
in a previous video,

129
00:06:16,002 --> 00:06:19,615
about the Three Layer Design
Model: the access layer,

130
00:06:19,615 --> 00:06:21,282
which is what gives access
to the network devices,

131
00:06:21,282 --> 00:06:23,270
like your laptops and your tablets,

132
00:06:23,270 --> 00:06:26,938
and then the distribution
layer, and then the core layer.

133
00:06:26,938 --> 00:06:29,234
So what we're really talking
about here is routers

134
00:06:29,234 --> 00:06:31,250
that would fit in that core layer

135
00:06:31,250 --> 00:06:33,070
that would actually transmit traffic

136
00:06:33,070 --> 00:06:35,394
back and forth between agencies.

137
00:06:35,394 --> 00:06:38,306
So there would be a
router owned by the FBI

138
00:06:38,306 --> 00:06:40,714
that would be connected to
a router owned by the CIA,

139
00:06:40,714 --> 00:06:42,298
that'd be connected to a router owned

140
00:06:42,298 --> 00:06:44,202
by the Social Security Administration,

141
00:06:44,202 --> 00:06:46,498
and those would be
considered backbone routers,

142
00:06:46,498 --> 00:06:49,690
they form the backbone of
the federal governments

143
00:06:49,690 --> 00:06:51,986
and how they communicate to each other.

144
00:06:51,986 --> 00:06:54,842
So back in 2008, the US
Federal Government said

145
00:06:54,842 --> 00:06:59,238
that all of those devices
have to be IPv6 capable.

146
00:06:59,238 --> 00:07:02,570
Now get that, they didn't
say we have to configure IPv6

147
00:07:02,570 --> 00:07:05,006
on those devices and run IPv6,

148
00:07:05,006 --> 00:07:07,694
they just said whatever
hardware and software

149
00:07:07,694 --> 00:07:11,027
is on those devices has to support IPv6.

150
00:07:12,958 --> 00:07:15,870
So back in 2008, there was
a lot of purchasing going on

151
00:07:15,870 --> 00:07:18,138
to get some new software, new equipment

152
00:07:18,138 --> 00:07:21,862
to make sure that that
requirement would be met.

153
00:07:21,862 --> 00:07:25,362
Now, just last year, in September of 2015,

154
00:07:26,258 --> 00:07:28,806
the American Registry of Internet Numbers,

155
00:07:28,806 --> 00:07:32,054
the regional internet registry
that supports North America,

156
00:07:32,054 --> 00:07:34,221
ran out of IPv4 addresses.

157
00:07:35,834 --> 00:07:38,018
So remember when I was first
talking about IP addressing?

158
00:07:38,018 --> 00:07:40,792
I was saying, "Well,
sometimes you can just skip

159
00:07:40,792 --> 00:07:42,346
your service provider and go directly

160
00:07:42,346 --> 00:07:44,054
to your regional internet registry

161
00:07:44,054 --> 00:07:47,162
and get provider independent addressing?"

162
00:07:47,162 --> 00:07:49,262
can't do that with ARIN any more.

163
00:07:49,262 --> 00:07:51,950
They actually have a few
addresses they've held in reserve

164
00:07:51,950 --> 00:07:53,910
for very special-use cases,

165
00:07:53,910 --> 00:07:56,178
but it's next to impossible for you

166
00:07:56,178 --> 00:07:57,942
to justify getting those.

167
00:07:57,942 --> 00:08:01,498
So ARIN has basically run
out of IPv4 addresses,

168
00:08:01,498 --> 00:08:03,710
so here, in the United States and Canada,

169
00:08:03,710 --> 00:08:07,042
at this point, all the service
providers have gobbled up

170
00:08:07,042 --> 00:08:10,206
whatever remaining IPv4
addresses are left.

171
00:08:10,206 --> 00:08:13,958
And there's none at any
tiers higher than them.

172
00:08:13,958 --> 00:08:15,722
So that's where we are today

173
00:08:15,722 --> 00:08:18,186
and I was just looking at
some internet statistics

174
00:08:18,186 --> 00:08:20,062
before I recorded this video,

175
00:08:20,062 --> 00:08:21,714
and it's actually surprising me

176
00:08:21,714 --> 00:08:25,046
because about, oh, 15 years ago or so,

177
00:08:25,046 --> 00:08:27,538
so around 2000, so this is right around

178
00:08:27,538 --> 00:08:30,450
when the first RFC for IPv6 was written,

179
00:08:30,450 --> 00:08:32,494
everybody was pretty much laughing it off.

180
00:08:32,494 --> 00:08:35,378
They said, "Ah, we're never
gonna run out of IPv4 addresses,

181
00:08:35,378 --> 00:08:38,178
"this thing's too much work,
too hard to understand,

182
00:08:38,178 --> 00:08:39,802
"we're not gonna deal with it."

183
00:08:39,802 --> 00:08:43,134
So for the longest time,
year after year after year,

184
00:08:43,134 --> 00:08:45,514
people were pushing back on IPv6 saying,

185
00:08:45,514 --> 00:08:49,154
"Oh, it's gonna be
decades before it's used."

186
00:08:49,154 --> 00:08:52,758
And they were saying, "Oh," I
think as early as like 2012,

187
00:08:52,758 --> 00:08:56,925
or 2013, not that long ago,
IPv6 traffic on the internet,

188
00:08:58,162 --> 00:09:00,038
so if you take a look at all the traffic

189
00:09:00,038 --> 00:09:01,802
running across the internet globally,

190
00:09:01,802 --> 00:09:04,070
at that point in time,
like two, three years ago,

191
00:09:04,070 --> 00:09:07,430
IPv6 traffic was like one percent.

192
00:09:07,430 --> 00:09:10,482
Maybe not even one
percent, it was so small.

193
00:09:10,482 --> 00:09:12,750
Well I just looked at
some statistics online

194
00:09:12,750 --> 00:09:16,278
that now say that IPv6
running across the internet

195
00:09:16,278 --> 00:09:18,938
is as high as 20 percent.

196
00:09:18,938 --> 00:09:21,614
Think about that, one
out of every five packets

197
00:09:21,614 --> 00:09:24,246
that's going across the
internet now globally

198
00:09:24,246 --> 00:09:26,010
is an IPv6 packet.

199
00:09:26,010 --> 00:09:28,978
It is ramping up really, really quickly.

200
00:09:28,978 --> 00:09:30,994
So if you're gonna go
into the networking fields

201
00:09:30,994 --> 00:09:33,762
and engineer an admin,
you can no longer afford

202
00:09:33,762 --> 00:09:37,990
to ignore IPv6, it will
be a part of your life.

203
00:09:37,990 --> 00:09:39,978
It is here, it is now!

204
00:09:39,978 --> 00:09:42,022
So, that being the case,

205
00:09:42,022 --> 00:09:43,998
also I found this website right here

206
00:09:43,998 --> 00:09:45,594
that I thought was kinda interesting

207
00:09:45,594 --> 00:09:46,882
that I wanna share with you.

208
00:09:46,882 --> 00:09:49,990
This is IPv6.com, you could go there

209
00:09:49,990 --> 00:09:51,754
and if you scroll down a little bit,

210
00:09:51,754 --> 00:09:54,274
this is under the history and timeline,

211
00:09:54,274 --> 00:09:55,982
it shows you right here,

212
00:09:55,982 --> 00:09:57,802
look at this chart right in the middle.

213
00:09:57,802 --> 00:10:01,969
So this shows how the address
depletion of IPv4 went.

214
00:10:04,130 --> 00:10:05,963
So back in 1985, 1985!

215
00:10:07,070 --> 00:10:10,290
So this is just like three or four years

216
00:10:10,290 --> 00:10:12,175
after IP was invented.

217
00:10:12,175 --> 00:10:15,442
Already one sixteenth of
the total address space

218
00:10:15,442 --> 00:10:18,382
of those billions of addresses
were already consumed.

219
00:10:18,382 --> 00:10:22,638
And then in 2000, fifteen,
sixteen years ago,

220
00:10:22,638 --> 00:10:25,382
half of the address space was used

221
00:10:25,382 --> 00:10:27,370
and then in that same year 2000,

222
00:10:27,370 --> 00:10:29,218
two thirds of the address space.

223
00:10:29,218 --> 00:10:31,038
Actually, halfway through 2002.

224
00:10:31,038 --> 00:10:33,978
And now here we are in 2016,

225
00:10:33,978 --> 00:10:37,422
you can imagine it's, it's
virtually gone at this point.

226
00:10:37,422 --> 00:10:41,589
So I found that to be a pretty
interesting document there.

227
00:10:42,574 --> 00:10:46,657
So now we have an idea as
to why IPv6 was needed,

228
00:10:48,090 --> 00:10:50,414
it was because they were
running out of addresses.

229
00:10:50,414 --> 00:10:54,247
Okay, so, what does an
IPv6 address look like?

230
00:10:55,258 --> 00:10:58,002
The main change with IPv6 is

231
00:10:58,002 --> 00:11:02,734
that the address is four times
as big as an IPv4 address;

232
00:11:02,734 --> 00:11:06,901
instead of 32-bits, it is
now 128-bits in size, so.

233
00:11:11,918 --> 00:11:14,494
That would be like an IPv6 address.

234
00:11:14,494 --> 00:11:16,342
Now I didn't actually count those bits,

235
00:11:16,342 --> 00:11:18,918
I'm not exactly sure if that's 128 or not,

236
00:11:18,918 --> 00:11:23,090
but in binary, it's a
massively large number.

237
00:11:23,090 --> 00:11:26,562
As a matter of fact, I heard
someone say a long time ago

238
00:11:26,562 --> 00:11:30,202
that if you think of
two to the power or 128,

239
00:11:30,202 --> 00:11:32,386
that's how many combinations
of addresses there are,

240
00:11:32,386 --> 00:11:34,794
I don't think there's
even a name for that.

241
00:11:34,794 --> 00:11:36,630
Somebody said that there were so many

242
00:11:36,630 --> 00:11:38,674
IPv6 addresses available

243
00:11:38,674 --> 00:11:43,406
that every person could
have a unique IPV6 address

244
00:11:43,406 --> 00:11:45,646
for every single hair on their head,

245
00:11:45,646 --> 00:11:49,202
and there would still be an
infinite amount left over.

246
00:11:49,202 --> 00:11:53,178
So, hopefully, unless we
expand throughout the galaxy

247
00:11:53,178 --> 00:11:55,698
like Star Trek and
populate distant planets,

248
00:11:55,698 --> 00:11:59,562
we'll be with IPv6 for a long, long time.

249
00:11:59,562 --> 00:12:02,110
So, we know that in IPv4,

250
00:12:02,110 --> 00:12:05,974
that binary number was divided
into octets, into bites.

251
00:12:05,974 --> 00:12:09,166
We have four bites, and
then each bite was converted

252
00:12:09,166 --> 00:12:13,030
into a decimal number, and
then separated by a dot.

253
00:12:13,030 --> 00:12:14,626
So that was dot a decimal.

254
00:12:14,626 --> 00:12:17,118
They could have done that with this,

255
00:12:17,118 --> 00:12:19,890
but they chose a different approach.

256
00:12:19,890 --> 00:12:24,057
They chose to represent
these as hexadecimal numbers.

257
00:12:25,490 --> 00:12:26,554
Hexadecimal?

258
00:12:26,554 --> 00:12:27,734
That's right, I know, we haven't talked

259
00:12:27,734 --> 00:12:29,078
about hexadecimal yet.

260
00:12:29,078 --> 00:12:33,245
So now, I need to do a
quick primer on hexadecimal.

261
00:12:34,846 --> 00:12:35,926
It's actually not that hard.

262
00:12:35,926 --> 00:12:39,948
I hope it will not be that hard for you.

263
00:12:39,948 --> 00:12:43,962
So remember, let's go back
to our binary tutorial

264
00:12:43,962 --> 00:12:46,790
and our decimal tutorial,
'member how we said that

265
00:12:46,790 --> 00:12:49,506
you have a single placeholder,

266
00:12:49,506 --> 00:12:53,286
and how many potential digits
could go in there depends

267
00:12:53,286 --> 00:12:56,030
on what numbering system you're using.

268
00:12:56,030 --> 00:12:58,550
If you're using base 10 decimal,

269
00:12:58,550 --> 00:13:00,781
that means you have 10 possible things

270
00:13:00,781 --> 00:13:04,574
that could go in here, from a
zero through a nine, base 10.

271
00:13:04,574 --> 00:13:07,570
If you're using binary, it was base two.

272
00:13:07,570 --> 00:13:09,502
Which means you had two
possible combinations,

273
00:13:09,502 --> 00:13:10,835
a zero or a one.

274
00:13:11,826 --> 00:13:13,243
Well, hexadecimal

275
00:13:16,758 --> 00:13:18,925
is a base 16 system, what?

276
00:13:21,325 --> 00:13:24,566
I know, it's so weird, but
actually, it's a base 16 system.

277
00:13:24,566 --> 00:13:26,414
So in this one placeholder,

278
00:13:26,414 --> 00:13:30,082
you have 16 possible things
that could go in there.

279
00:13:30,082 --> 00:13:31,818
What could those possibly be?

280
00:13:31,818 --> 00:13:35,985
Well, let me make my font
here a little bit smaller.

281
00:13:37,390 --> 00:13:39,910
The first 10 digits in hexadecimal

282
00:13:39,910 --> 00:13:43,242
are exactly the same as in decimal.

283
00:13:43,242 --> 00:13:44,409
You have zero,

284
00:13:46,658 --> 00:13:49,710
through nine, so that covers the first 10

285
00:13:49,710 --> 00:13:52,874
out of my 16 possible
characters, that's no different.

286
00:13:52,874 --> 00:13:54,386
And then for the remaining
characters, we use letters.

287
00:13:54,386 --> 00:13:58,110
So A is the equivalent of 10 in decimal,

288
00:13:58,110 --> 00:14:02,277
B is the equivalent of 11,
C is the equivalent of 12,

289
00:14:08,453 --> 00:14:10,006
D, I'm running out of space here.

290
00:14:10,006 --> 00:14:12,339
All right, hold on a second.

291
00:14:16,094 --> 00:14:19,011
Okay, so we have zero through nine,

292
00:14:21,582 --> 00:14:24,522
and then we have our letters.

293
00:14:24,522 --> 00:14:26,605
A equals 10, B equals 11,

294
00:14:28,586 --> 00:14:30,669
C equals 12, D equals 13,

295
00:14:32,562 --> 00:14:35,645
E equals 14, and lastly, F equals 15.

296
00:14:38,442 --> 00:14:42,609
So that give us our 16 possible
characters from zero to F,

297
00:14:44,574 --> 00:14:47,542
that's 16 possible combinations.

298
00:14:47,542 --> 00:14:51,709
And also, remember, when we
were talking about decimal,

299
00:14:52,666 --> 00:14:55,438
if I had a three-digit number,

300
00:14:55,438 --> 00:14:59,806
the first position was
always the ones position,

301
00:14:59,806 --> 00:15:02,774
and then depending on what
base system we were using

302
00:15:02,774 --> 00:15:04,762
determined what he next one was.

303
00:15:04,762 --> 00:15:07,142
So in decimal, we just
kept multiplying by 10's.

304
00:15:07,142 --> 00:15:09,018
So we had the 10's position next,

305
00:15:09,018 --> 00:15:11,874
10 times 10 is 100, so on and so forth.

306
00:15:11,874 --> 00:15:13,974
With binary, is multiplying by two.

307
00:15:13,974 --> 00:15:17,334
So we had the ones and then
we had the twos position,

308
00:15:17,334 --> 00:15:20,106
two times two is four,
four times two is eight,

309
00:15:20,106 --> 00:15:22,878
well you can probably see
where I'm going with this.

310
00:15:22,878 --> 00:15:26,045
With hexadecimal, we multiply by 16's.

311
00:15:27,442 --> 00:15:29,178
So we have the ones position,

312
00:15:29,178 --> 00:15:32,846
and then the next one
is the 16's position,

313
00:15:32,846 --> 00:15:35,263
and 16 times 16 is the 256's,

314
00:15:36,934 --> 00:15:39,146
and after that I can't do it from memory.

315
00:15:39,146 --> 00:15:41,498
(lightly chuckles) I can
only do three positions.

316
00:15:41,498 --> 00:15:45,838
So with the way a hexadecimal
number would look,

317
00:15:45,838 --> 00:15:47,518
they're not always represented this way,

318
00:15:47,518 --> 00:15:51,970
but if you ever see a number
that says 0 x something,

319
00:15:51,970 --> 00:15:54,686
that's representing a hexadecimal number.

320
00:15:54,686 --> 00:15:56,519
So for example, 0x003,

321
00:16:02,498 --> 00:16:03,898
well that's just the number three.

322
00:16:03,898 --> 00:16:05,746
It's no different than in decimal.

323
00:16:05,746 --> 00:16:09,913
But if I say 0x00a, that's
the number 10 in hexadecimal.

324
00:16:13,390 --> 00:16:14,640
Or I could say,

325
00:16:16,106 --> 00:16:18,402
and usually the leading
zeros are left off.

326
00:16:18,402 --> 00:16:20,642
So if i was gonna give you
the hexadecimal number of 10,

327
00:16:20,642 --> 00:16:22,392
I would just say 0xa.

328
00:16:23,750 --> 00:16:26,158
There's only one character,

329
00:16:26,158 --> 00:16:28,902
so that one character has
to be in the ones position,

330
00:16:28,902 --> 00:16:32,542
so that's 10 times one, which is 10.

331
00:16:32,542 --> 00:16:34,209
Or I could say 0x1b,

332
00:16:38,534 --> 00:16:41,866
well that means I've got
a b in the ones position

333
00:16:41,866 --> 00:16:44,449
and a one in the 16's position,

334
00:16:45,394 --> 00:16:48,061
so that's 16 plus 11, that's 27.

335
00:16:51,716 --> 00:16:53,549
0x1b is 27 in decimal.

336
00:16:57,126 --> 00:16:57,959
Or,

337
00:16:58,946 --> 00:16:59,779
I could go

338
00:17:00,934 --> 00:17:01,767
0x1a3,

339
00:17:07,794 --> 00:17:09,026
that's gonna be a pretty big number.

340
00:17:09,026 --> 00:17:12,918
So that means I have a
three in the ones position,

341
00:17:12,918 --> 00:17:16,670
I have a 'a' which is
10 in the 16's position,

342
00:17:16,670 --> 00:17:19,170
and I have a one in the 256's.

343
00:17:20,394 --> 00:17:22,061
So that would be 256

344
00:17:22,998 --> 00:17:25,998
plus 160 because 10 times 16 is 160,

345
00:17:28,990 --> 00:17:29,907
plus three.

346
00:17:31,678 --> 00:17:33,274
Im not gonna add that up in my head,

347
00:17:33,274 --> 00:17:34,478
but whatever number that is,

348
00:17:34,478 --> 00:17:38,311
that would be the decimal
equivalent of 0x1a3.

349
00:17:40,022 --> 00:17:43,774
So how does this relate
to an IPv6 address?

350
00:17:43,774 --> 00:17:47,941
Alright, so let me actually
write a real IPv6 address.

351
00:17:55,718 --> 00:17:56,635
That's one,

352
00:17:59,574 --> 00:18:00,407
two,

353
00:18:03,746 --> 00:18:04,579
three,

354
00:18:05,946 --> 00:18:07,822
four, I'm not gonna do the whole thing,

355
00:18:07,822 --> 00:18:10,239
I'm just gonna do some of it.

356
00:18:12,498 --> 00:18:14,165
Okay, so in reality,

357
00:18:15,494 --> 00:18:19,162
an actual IPv6 address would
have eight of these things,

358
00:18:19,162 --> 00:18:22,214
I've drawn one, two, three,
four, I've drawn five.

359
00:18:22,214 --> 00:18:25,966
So, still a little bit left over but,

360
00:18:25,966 --> 00:18:27,422
not gonna worry about that right now.

361
00:18:27,422 --> 00:18:30,390
So, how do we actually
convert this into a number

362
00:18:30,390 --> 00:18:32,126
that we can read?

363
00:18:32,126 --> 00:18:36,410
Well, what you would do is,
starting from left to right,

364
00:18:36,410 --> 00:18:39,993
you would take every
four binary characters

365
00:18:41,366 --> 00:18:43,962
and convert that into a hex character.

366
00:18:43,962 --> 00:18:48,330
So that is, in decimal,
that's the number two, right?

367
00:18:48,330 --> 00:18:51,270
The ones is off, the two
is on, the four is off,

368
00:18:51,270 --> 00:18:54,322
and the eight is off, so
that's the number two.

369
00:18:54,322 --> 00:18:57,822
And then we do it again with the next one.

370
00:18:59,194 --> 00:19:01,462
The next four, that's pretty easy,

371
00:19:01,462 --> 00:19:04,122
that's just the number zero,

372
00:19:04,122 --> 00:19:08,322
and then we do it again
with the next four.

373
00:19:08,322 --> 00:19:11,206
So we've got the ones position turned on,

374
00:19:11,206 --> 00:19:15,042
and the eights position
turn on, so that's nine.

375
00:19:15,042 --> 00:19:17,982
And then we do it one more time.

376
00:19:17,982 --> 00:19:22,518
Now, in decimal, we've got
the eight and the four.

377
00:19:22,518 --> 00:19:24,338
So that's the number 12.

378
00:19:24,338 --> 00:19:28,171
But in hexadecimal, we
don't say 12, we say C.

379
00:19:29,994 --> 00:19:33,827
So, so far, I've represented
16-bits in binary

380
00:19:35,314 --> 00:19:38,674
by using four hexadecimal characters.

381
00:19:38,674 --> 00:19:40,130
And here's why that's important:

382
00:19:40,130 --> 00:19:42,380
after every 16 binary bits,

383
00:19:43,266 --> 00:19:47,433
or after every four hexadecimal
characters, we put a colon,

384
00:19:49,790 --> 00:19:51,373
and then we repeat.

385
00:19:52,730 --> 00:19:54,313
So this'll be zero,

386
00:19:55,222 --> 00:19:56,305
this'll be F,

387
00:19:57,882 --> 00:20:00,382
I gotta put a box around here,

388
00:20:01,242 --> 00:20:06,114
zero, so this one here is F
'cause that's the number 15,

389
00:20:06,114 --> 00:20:10,790
this one right here, we're
back to the number 12 again,

390
00:20:10,790 --> 00:20:13,170
no, that's the number 10
actually, the eight and the two,

391
00:20:13,170 --> 00:20:17,337
so that would be an 'a',
and then this here is a two,

392
00:20:18,350 --> 00:20:20,350
and then we put a colon.

393
00:20:22,858 --> 00:20:24,441
So an IPv6 address,

394
00:20:25,406 --> 00:20:29,438
because we clearly don't
represent it in binary,

395
00:20:29,438 --> 00:20:31,986
is represented as hexadecimal.

396
00:20:31,986 --> 00:20:34,898
So this is what an IPv6 address
would actually look like,

397
00:20:34,898 --> 00:20:37,810
I can actually fit this one in here.

398
00:20:37,810 --> 00:20:40,134
Two, I'm just gonna make up one.

399
00:20:40,134 --> 00:20:42,634
2001:00a5:0000:55ea:bbbb:cccc:

400
00:20:52,318 --> 00:20:53,410
now there's gonna be eight of these,

401
00:20:53,410 --> 00:20:56,434
one, two, three, four, five, six,

402
00:20:56,434 --> 00:20:58,517
1111, that's seven, 000c.

403
00:21:03,098 --> 00:21:06,150
So that is an IPv6 address.

404
00:21:06,150 --> 00:21:07,354
And if we actually did the math,

405
00:21:07,354 --> 00:21:09,706
you'd see that this is 128-bits in binary.

406
00:21:09,706 --> 00:21:14,106
Each one of these characters
represents 4-bits.

407
00:21:14,106 --> 00:21:16,598
Remember, here's the two,
there's 4-bits for that,

408
00:21:16,598 --> 00:21:18,866
here's a zero, that's 4-bits for that,

409
00:21:18,866 --> 00:21:22,338
so if you count up all of these characters

410
00:21:22,338 --> 00:21:24,494
multiplied times four,

411
00:21:24,494 --> 00:21:28,358
that would give you 128-bits in binary.

412
00:21:28,358 --> 00:21:31,494
So that's how an IPv6
address is represented.

413
00:21:31,494 --> 00:21:34,014
You have four hexadecimal characters,

414
00:21:34,014 --> 00:21:36,646
a colon, and then repeat.

415
00:21:36,646 --> 00:21:38,074
And then you'll have a maximum of eight

416
00:21:38,074 --> 00:21:40,574
of these groupings right here.

417
00:21:42,274 --> 00:21:45,382
Actually, I've heard, you know how we say,

418
00:21:45,382 --> 00:21:48,182
I'll write this on here,

419
00:21:48,182 --> 00:21:50,849
you know how we say that 1-unit,

420
00:21:52,970 --> 00:21:55,303
I'll just say, equals a bit.

421
00:21:56,486 --> 00:21:58,569
And 8-bits equals a byte,

422
00:22:00,798 --> 00:22:04,298
well, 16-bits equals what's called a word.

423
00:22:08,134 --> 00:22:09,634
So this is a word.

424
00:22:12,810 --> 00:22:16,618
So you have a colon after every word.

425
00:22:16,618 --> 00:22:19,201
Alright, let's go back to here.

426
00:22:22,218 --> 00:22:26,250
Expressed in hexadecimal
instead of decimal.

427
00:22:26,250 --> 00:22:29,554
4-bits equals one hexadecimal character.

428
00:22:29,554 --> 00:22:30,730
And there's an example.

429
00:22:30,730 --> 00:22:34,022
Now before I stop, there are ways,

430
00:22:34,022 --> 00:22:37,214
if the IPv6 address
takes a certain format,

431
00:22:37,214 --> 00:22:41,162
there are ways to make it
shorter, make it more manageable.

432
00:22:41,162 --> 00:22:43,850
And I'm gonna teach you
what those two tricks are

433
00:22:43,850 --> 00:22:44,767
to do that.

434
00:22:48,498 --> 00:22:51,886
And it all has to do
with consecutive zeros.

435
00:22:51,886 --> 00:22:53,902
What you're looking for in an IPv6 address

436
00:22:53,902 --> 00:22:56,478
to make it shorter are consecutive zeros.

437
00:22:56,478 --> 00:22:59,614
So let me give you a IPv6 address 2001,

438
00:22:59,614 --> 00:23:02,781
and I'm gonna put some spaces in here.

439
00:23:08,238 --> 00:23:11,571
One, two, three, four, five, six, seven.

440
00:23:12,746 --> 00:23:17,366
Okay, so here is the format
for making this shorter.

441
00:23:17,366 --> 00:23:19,382
So the first thing you would look for

442
00:23:19,382 --> 00:23:21,342
in a long address like this

443
00:23:21,342 --> 00:23:25,430
is I would look for a long
string of contiguous zeros.

444
00:23:25,430 --> 00:23:27,978
And what I mean by that
is look at the address

445
00:23:27,978 --> 00:23:31,086
and ask yourself, "Is there any word,"

446
00:23:31,086 --> 00:23:32,878
and remember, what do I mean by word,

447
00:23:32,878 --> 00:23:37,190
this is a word, this is a
word, that's a word, okay?

448
00:23:37,190 --> 00:23:39,626
So you look at your IPv6
address, and you say,

449
00:23:39,626 --> 00:23:43,406
"Is there any word that
begins with a zero?"

450
00:23:43,406 --> 00:23:45,336
I'll just put some arrows
on the ones that do,

451
00:23:45,336 --> 00:23:49,350
yup, that one does, that
one does, that one does,

452
00:23:49,350 --> 00:23:52,767
that one does, that one does, okay, next.

453
00:23:54,334 --> 00:23:58,198
Is there any place in this IPv6 address

454
00:23:58,198 --> 00:24:01,222
where we have a long
contiguous string of zeros?

455
00:24:01,222 --> 00:24:04,834
Where it starts at a
word and keeps on going.

456
00:24:04,834 --> 00:24:06,346
Well, actually we do.

457
00:24:06,346 --> 00:24:08,754
We have a couple places in here like that.

458
00:24:08,754 --> 00:24:11,694
Here's one that starts at a word

459
00:24:11,694 --> 00:24:13,277
and keeps on going.

460
00:24:14,214 --> 00:24:15,950
Here's one that start with a word

461
00:24:15,950 --> 00:24:17,533
and keeps on going.

462
00:24:19,002 --> 00:24:21,298
Now when you look at that,

463
00:24:21,298 --> 00:24:24,098
each one of those things
can be condensed down

464
00:24:24,098 --> 00:24:28,265
by using a special character
which is the double colon.

465
00:24:30,418 --> 00:24:32,810
But here's the rule
about the double colon.

466
00:24:32,810 --> 00:24:36,477
It can only be used
once in an IPv6 address.

467
00:24:37,850 --> 00:24:40,734
Let me give you the logic
behind why that's true.

468
00:24:40,734 --> 00:24:43,002
Let's say theoretically
that I could use it twice.

469
00:24:43,002 --> 00:24:47,169
Let's say I could do this:
2001, and then colon, colon,

470
00:24:49,274 --> 00:24:50,857
30 colon eaf0 colon

471
00:24:56,798 --> 00:24:58,842
and then we'll just say

472
00:24:58,842 --> 00:25:00,425
colon, colon, 2004.

473
00:25:03,266 --> 00:25:04,498
Let's say theoretically,

474
00:25:04,498 --> 00:25:08,670
that I could type in an IPv6
address like this on my laptop.

475
00:25:08,670 --> 00:25:09,874
Alright, now remember,

476
00:25:09,874 --> 00:25:12,170
when you're entering an
IPv6 address into a system,

477
00:25:12,170 --> 00:25:16,622
that system is expecting
you to give it 128-bits.

478
00:25:16,622 --> 00:25:19,086
Now it knows that you're
typing it in in hexadecimal.

479
00:25:19,086 --> 00:25:22,334
But for every letter or
every character you type in,

480
00:25:22,334 --> 00:25:24,070
it's saying, "Okay, there's 4-bits,

481
00:25:24,070 --> 00:25:25,246
"there's another 4-bits."

482
00:25:25,246 --> 00:25:26,870
it's converting it to binary.

483
00:25:26,870 --> 00:25:28,970
So if I typed it in like this,

484
00:25:28,970 --> 00:25:31,182
here's how my system would interpret this.

485
00:25:31,182 --> 00:25:32,849
It would say, "Okay,

486
00:25:33,898 --> 00:25:38,065
"What we've got here is we've
got one, two, three, four,

487
00:25:39,606 --> 00:25:40,614
"so this is very easy,

488
00:25:40,614 --> 00:25:43,946
"the human being has
provided us all 16-bits

489
00:25:43,946 --> 00:25:46,466
"of that word, all right.

490
00:25:46,466 --> 00:25:49,058
"And then we've got one, two, all right,

491
00:25:49,058 --> 00:25:52,586
"so we've got 8-bits of that word,

492
00:25:52,586 --> 00:25:54,098
"we're missing some stuff,

493
00:25:54,098 --> 00:25:58,181
"and then here we've got
another 16-bits of that,

494
00:26:00,647 --> 00:26:02,190
"and then down here,

495
00:26:02,190 --> 00:26:05,942
"we've got another
16-bits supplied to us."

496
00:26:05,942 --> 00:26:07,902
Okay, now the system would say,

497
00:26:07,902 --> 00:26:09,722
"Hmm, okay, let me add this up here.

498
00:26:09,722 --> 00:26:13,139
"16 times three is 48, plus eight is 56."

499
00:26:15,490 --> 00:26:17,407
so my laptop would say,

500
00:26:19,185 --> 00:26:20,768
"This idiotic human

501
00:26:23,162 --> 00:26:24,662
"has only given me

502
00:26:25,822 --> 00:26:27,655
"56-bits of an address

503
00:26:29,714 --> 00:26:31,797
"that requires 128-bits!"

504
00:26:34,194 --> 00:26:36,182
and so the system would say,

505
00:26:36,182 --> 00:26:37,658
"All right, I guess I can assume

506
00:26:37,658 --> 00:26:40,710
"that the remaining bits that
are left over are zeros."

507
00:26:40,710 --> 00:26:44,098
But, so okay, how many
bits are left over here?

508
00:26:44,098 --> 00:26:46,002
I don't have my calculator in front of me,

509
00:26:46,002 --> 00:26:48,074
so let's just do this real quick here

510
00:26:48,074 --> 00:26:50,622
'cause I can't do that in
my head quickly enough.

511
00:26:50,622 --> 00:26:52,455
So 128 minus 56 is 72.

512
00:26:55,746 --> 00:26:57,762
So there's 72-bits missing.

513
00:26:57,762 --> 00:26:59,134
So what if the system said,

514
00:26:59,134 --> 00:27:03,502
"Alright, I'm gonna
put maybe 70 zeros here

515
00:27:03,502 --> 00:27:05,042
"and two zeros here,

516
00:27:05,042 --> 00:27:06,974
"or maybe I should split it up equally,

517
00:27:06,974 --> 00:27:09,746
"36 zeros here, and 36 zeros here."

518
00:27:09,746 --> 00:27:13,274
You can see that if it
actually allowed you

519
00:27:13,274 --> 00:27:15,322
to put in double colons, there's
no way you could figure out

520
00:27:15,322 --> 00:27:18,542
where these zeros were supposed to be.

521
00:27:18,542 --> 00:27:20,446
It just could not figure that out.

522
00:27:20,446 --> 00:27:24,590
That's why we can only put
in the double colons once.

523
00:27:24,590 --> 00:27:27,194
And so when selecting it,

524
00:27:27,194 --> 00:27:30,330
it makes sense to only put
the double colons to represent

525
00:27:30,330 --> 00:27:33,018
the biggest string of contiguous zeros.

526
00:27:33,018 --> 00:27:35,006
If I'm trying to shorten this thing down,

527
00:27:35,006 --> 00:27:37,946
it makes more sense to
represent this big long thing

528
00:27:37,946 --> 00:27:41,390
with the double colon, than
it does to represent this.

529
00:27:41,390 --> 00:27:44,246
So let's shorten it down
a little bit right now.

530
00:27:44,246 --> 00:27:46,413
So 2001, 0000, 0030, eaf0,

531
00:27:53,066 --> 00:27:54,382
and then I'm gonna do

532
00:27:54,382 --> 00:27:57,632
a double colon to represent that, 2004.

533
00:27:59,973 --> 00:28:01,595
So so far, I've been able
to shorten it to this,

534
00:28:01,595 --> 00:28:03,678
I'll put it all together.

535
00:28:05,926 --> 00:28:10,093
So already, you can see that
this is much shorter than this,

536
00:28:12,198 --> 00:28:15,210
just by taking this long
contiguous string of zeros

537
00:28:15,210 --> 00:28:17,338
and condensing it down
with a double colon.

538
00:28:17,338 --> 00:28:19,158
Now I'm gonna emphasize this.

539
00:28:19,158 --> 00:28:23,414
I had to start with a word
that began with a zero,

540
00:28:23,414 --> 00:28:25,990
because you might be wondering,
why did I start right here?

541
00:28:25,990 --> 00:28:28,650
Because that's not
considered a leading zero,

542
00:28:28,650 --> 00:28:30,330
that is a trailing zero,

543
00:28:30,330 --> 00:28:33,214
it trails at the tail end of the word.

544
00:28:33,214 --> 00:28:36,182
I need a zero that leads the word,

545
00:28:36,182 --> 00:28:38,870
and then a string of zeros after that.

546
00:28:38,870 --> 00:28:41,558
That's why I had to start right here.

547
00:28:41,558 --> 00:28:45,170
So that's one thing, a long
contiguous string of zeros

548
00:28:45,170 --> 00:28:47,018
that starts with a word

549
00:28:47,018 --> 00:28:49,930
can be replaced with a double colon.

550
00:28:49,930 --> 00:28:51,554
There's one other thing.

551
00:28:51,554 --> 00:28:53,682
After you have what's left,

552
00:28:53,682 --> 00:28:57,574
look and ask yourself, "Do
I have any remaining words

553
00:28:57,574 --> 00:29:00,157
"that still start with a zero?"

554
00:29:01,158 --> 00:29:04,686
Well, yeah, that one starts with a zero,

555
00:29:04,686 --> 00:29:07,458
that one starts with a zero.

556
00:29:07,458 --> 00:29:08,958
So in those words,

557
00:29:10,202 --> 00:29:13,785
we can get rid of all
of the leading zeros.

558
00:29:16,026 --> 00:29:17,790
So I'm gonna out a line through them.

559
00:29:17,790 --> 00:29:21,402
Those three zeros and that
word we can get rid of.

560
00:29:21,402 --> 00:29:22,886
Can't get rid of the zero at the end,

561
00:29:22,886 --> 00:29:24,258
'cause that's a trailing zero,

562
00:29:24,258 --> 00:29:26,106
and we can get rid of these two zeros

563
00:29:26,106 --> 00:29:29,354
because these are leading zeros.

564
00:29:29,354 --> 00:29:30,894
So in its final form,

565
00:29:30,894 --> 00:29:35,061
in its shortest form I
could possibly come up with,

566
00:29:37,923 --> 00:29:40,022
so I've now taken it from this black

567
00:29:40,022 --> 00:29:43,130
down all the way to
this one here in green.

568
00:29:43,130 --> 00:29:44,698
And that is the shortest way

569
00:29:44,698 --> 00:29:47,448
I could condense an IPv6 address.

570
00:29:49,206 --> 00:29:52,370
Let me give you a couple that
you can pause the video on

571
00:29:52,370 --> 00:29:55,506
and practice and see if
you can get it right.

572
00:29:55,506 --> 00:29:56,551
You might wanna pause right now

573
00:29:56,551 --> 00:29:57,767
and take a screen shot of this

574
00:29:57,767 --> 00:30:00,517
before I move on to the next one.

575
00:30:03,826 --> 00:30:04,659
Okay.

576
00:30:14,454 --> 00:30:16,346
Okay, go ahead and pause the video,

577
00:30:16,346 --> 00:30:19,314
try to abbreviate or condense
this as much as possible

578
00:30:19,314 --> 00:30:22,506
using the rules I just talked
about and then press play

579
00:30:22,506 --> 00:30:26,398
when you think you've got your answer.

580
00:30:26,398 --> 00:30:29,730
Okay, so doing the way I
did, I would say, once again,

581
00:30:29,730 --> 00:30:33,874
look for any word that begins with a zero,

582
00:30:33,874 --> 00:30:36,291
that one does, that one does,

583
00:30:38,326 --> 00:30:40,743
that one does, that one does.

584
00:30:41,770 --> 00:30:45,937
At that point, look for a long
contiguous string of zeros

585
00:30:47,398 --> 00:30:48,490
beginning with a word,

586
00:30:48,490 --> 00:30:52,158
and this is the longest
string we have, right there.

587
00:30:52,158 --> 00:30:55,991
So I can get rid of that
with my double colon.

588
00:30:56,974 --> 00:30:59,858
And then with what's left over,

589
00:30:59,858 --> 00:31:02,658
draw a line through any
of the leading zeros

590
00:31:02,658 --> 00:31:04,142
of any of the remaining words.

591
00:31:04,142 --> 00:31:06,326
So I can get rid of those three,

592
00:31:06,326 --> 00:31:08,202
and that's it.

593
00:31:08,202 --> 00:31:10,274
So the smallest I could make this address

594
00:31:10,274 --> 00:31:14,441
would be 200e:0, gotta
leave in the trailing zero,

595
00:31:15,842 --> 00:31:19,090
4000, can't get rid of any of
those zeros behind the four

596
00:31:19,090 --> 00:31:22,870
because they're not
leading, they're trailing,

597
00:31:22,870 --> 00:31:24,037
600:eade:1100,

598
00:31:29,422 --> 00:31:33,134
so that is the smallest
that you could do that one.

599
00:31:33,134 --> 00:31:34,634
Let's do one more.

600
00:31:52,118 --> 00:31:53,798
Okay, go ahead and press pause

601
00:31:53,798 --> 00:31:56,631
and try to condense this one down.

602
00:31:58,362 --> 00:32:01,470
Okay, so once again, let's
take a look at any words

603
00:32:01,470 --> 00:32:04,102
that begin with a zero.

604
00:32:04,102 --> 00:32:06,519
That one does, that one does,

605
00:32:09,086 --> 00:32:12,419
actually, no, let me do the entire word.

606
00:32:13,790 --> 00:32:17,598
That one does, that one leads with zeros,

607
00:32:17,598 --> 00:32:19,082
that one leads with zeros,

608
00:32:19,082 --> 00:32:21,910
and this one leads with zeros, okay.

609
00:32:21,910 --> 00:32:26,810
So of this, where are my
contiguous string of zeros?

610
00:32:26,810 --> 00:32:29,806
Well, I've got one that starts
right here, that ends there,

611
00:32:29,806 --> 00:32:32,634
so that covers seven zeros,

612
00:32:32,634 --> 00:32:35,551
here's one that has just two zeros,

613
00:32:36,526 --> 00:32:38,776
another two, and then four.

614
00:32:39,886 --> 00:32:42,042
So I would say the seven zeros

615
00:32:42,042 --> 00:32:44,562
would be the best way to get rid of those.

616
00:32:44,562 --> 00:32:48,146
And then I'm gonna put a line
through the remaining ones,

617
00:32:48,146 --> 00:32:50,638
so I'm gonna be able to cut out those,

618
00:32:50,638 --> 00:32:53,018
'cause those are leading
zeros, cut out those,

619
00:32:53,018 --> 00:32:55,902
and I'll be able to cut out these three,

620
00:32:55,902 --> 00:32:57,652
leaving the last one.

621
00:32:59,374 --> 00:33:01,838
So in its final form, this
address will look like

622
00:33:01,838 --> 00:33:03,921
2560:1000:ea05::5:ea:3d:0

623
00:33:16,834 --> 00:33:19,334
(light music)