1
00:00:00,000 --> 00:00:07,160

2
00:00:07,160 --> 00:00:13,400
So let's kick off our discussion
of IS-IS support for IPv6

3
00:00:13,400 --> 00:00:18,800
by just doing a quick review
of some basic IPv6 principles.

4
00:00:18,800 --> 00:00:22,550
So we'll start off with
taking a look at how

5
00:00:22,550 --> 00:00:24,830
to do some address conversions.

6
00:00:24,830 --> 00:00:27,140
Just in case at
some point we need

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00:00:27,140 --> 00:00:32,060
to convert addresses from say
decimal to binary or binary

8
00:00:32,060 --> 00:00:37,430
to hex, since IPv6 uses
hexadecimal for its addressing,

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00:00:37,430 --> 00:00:39,440
this could be a useful skill.

10
00:00:39,440 --> 00:00:43,010
Then we'll take a look
at IPv6 addressing,

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00:00:43,010 --> 00:00:45,200
we'll go over how
it's formatted,

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00:00:45,200 --> 00:00:48,800
and the most important part
is how to properly shorten

13
00:00:48,800 --> 00:00:50,030
the addresses.

14
00:00:50,030 --> 00:00:54,020
We don't want to have to
type in 128-bit address

15
00:00:54,020 --> 00:00:56,420
every time we put
these into the routers.

16
00:00:56,420 --> 00:00:58,670
So we need to know
how to shorten them

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00:00:58,670 --> 00:01:01,640
but shorten them in a way
that we won't actually

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00:01:01,640 --> 00:01:03,500
alter the address itself.

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00:01:03,500 --> 00:01:06,560
So it has to be
shortened properly.

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00:01:06,560 --> 00:01:09,710
Then let's wrap up
with a quick discussion

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00:01:09,710 --> 00:01:11,660
of neighbor discovery.

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00:01:11,660 --> 00:01:16,640
IPv6 doesn't use ARP or
address resolution protocol

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00:01:16,640 --> 00:01:21,050
like IPv4 does, rather it
uses neighbor discovery.

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00:01:21,050 --> 00:01:24,020
So we'll do an overview
of that as well.

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00:01:24,020 --> 00:01:28,250
So let's jump in and start
by doing some decimal to hex

26
00:01:28,250 --> 00:01:31,670
and hex to binary
conversions so we understand

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00:01:31,670 --> 00:01:35,190
how these numbers correlate.

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00:01:35,190 --> 00:01:38,040
So to start off with,
we will do some decimal

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00:01:38,040 --> 00:01:39,990
to binary conversion.

30
00:01:39,990 --> 00:01:42,120
And we have a conversion
chart over here

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00:01:42,120 --> 00:01:45,900
just for convenience that just
lists out the binary values

32
00:01:45,900 --> 00:01:48,150
from the least
significant bit which

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00:01:48,150 --> 00:01:50,880
is the one over here
going over to the most

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00:01:50,880 --> 00:01:55,410
significant bit which, of
course, is represented by 128.

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00:01:55,410 --> 00:02:00,720
So the way we take a
decimal number say 137

36
00:02:00,720 --> 00:02:03,540
and we convert
this to binary, is

37
00:02:03,540 --> 00:02:07,320
we simply look at each digit
in our conversion chart

38
00:02:07,320 --> 00:02:09,539
and we ask if that's
greater than the number

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00:02:09,539 --> 00:02:10,740
we want to convert.

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00:02:10,740 --> 00:02:15,660
So for example in this case,
137 is greater than 128.

41
00:02:15,660 --> 00:02:18,720
So we would simply
put a one in this spot

42
00:02:18,720 --> 00:02:24,540
and subtract 128 from the value
that we're trying to convert.

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00:02:24,540 --> 00:02:27,030
The answer here,
of course, is 9.

44
00:02:27,030 --> 00:02:31,200
And then we look over and
we look at this 64 value.

45
00:02:31,200 --> 00:02:33,810
Is there a 64 in 9?

46
00:02:33,810 --> 00:02:36,780
And, of course, the answer
to this is going to be no.

47
00:02:36,780 --> 00:02:38,310
So this is a zero.

48
00:02:38,310 --> 00:02:42,180
Neither is there a 32 or a 16.

49
00:02:42,180 --> 00:02:44,598
Now, of course, there's an 8.

50
00:02:44,598 --> 00:02:46,890
And, of course, we don't
really have to spell this out.

51
00:02:46,890 --> 00:02:49,350
At this point the
math is fairly simple.

52
00:02:49,350 --> 00:02:52,320
But just for completeness,
this, of course,

53
00:02:52,320 --> 00:02:54,960
is going to come
down to the one.

54
00:02:54,960 --> 00:03:04,740
So what we end up with here
is 137 in binary is 10001001.

55
00:03:04,740 --> 00:03:08,430
So it's simply a matter of
subtracting each value that's

56
00:03:08,430 --> 00:03:10,170
in the original number.

57
00:03:10,170 --> 00:03:12,060
And, of course,
to convert it back

58
00:03:12,060 --> 00:03:14,680
we would do exactly
the opposite.

59
00:03:14,680 --> 00:03:23,560
Let's say we simply had
a value of 11011001.

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00:03:23,560 --> 00:03:27,520
To convert that back, we would
simply take the first value

61
00:03:27,520 --> 00:03:33,730
128, we would add the next
value which, of course, is 64,

62
00:03:33,730 --> 00:03:36,130
this is going to be 192.

63
00:03:36,130 --> 00:03:40,150
Then we add 16 to that, 208.

64
00:03:40,150 --> 00:03:44,290
We add 8 to that, which is 216.

65
00:03:44,290 --> 00:03:46,600
And then we add 1 to that.

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00:03:46,600 --> 00:03:50,260
And our grand total here is 217.

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00:03:50,260 --> 00:03:58,540
So 11011001 would
be 217 in decimal.

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00:03:58,540 --> 00:04:01,780
So next up let's take a
look at converting this

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00:04:01,780 --> 00:04:04,330
from binary to hex.

70
00:04:04,330 --> 00:04:07,330
So in this case, we'll
just use the same number.

71
00:04:07,330 --> 00:04:10,960
I just drove the 217 up
here to clear up some space.

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00:04:10,960 --> 00:04:15,130
To convert this to hex, what
we're essentially going to do

73
00:04:15,130 --> 00:04:17,649
is split the number in half.

74
00:04:17,649 --> 00:04:19,660
So we're going to
take our binary number

75
00:04:19,660 --> 00:04:22,990
and split it like
this, and then we're

76
00:04:22,990 --> 00:04:27,280
going to convert this section
of the number based off

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00:04:27,280 --> 00:04:29,740
of this part of the scale.

78
00:04:29,740 --> 00:04:33,580
So in other words, this
is going to become a one,

79
00:04:33,580 --> 00:04:37,360
this would be the two,
this would be the four,

80
00:04:37,360 --> 00:04:39,550
this would be the eight.

81
00:04:39,550 --> 00:04:47,350
So if we take our 8 plus our 4,
of course, that's 12, plus 1,

82
00:04:47,350 --> 00:04:53,080
we end up with 13 for the
left side of this number.

83
00:04:53,080 --> 00:04:56,110
For the other side, this
is fairly straightforward,

84
00:04:56,110 --> 00:04:59,200
we only have an 8 and a 1.

85
00:04:59,200 --> 00:05:02,200
So this side simply becomes 9.

86
00:05:02,200 --> 00:05:05,350
Now 9 fits, of course,
in a single digit.

87
00:05:05,350 --> 00:05:08,530
So part of our
answer here is going

88
00:05:08,530 --> 00:05:11,410
to be that this is
going to be a 9.

89
00:05:11,410 --> 00:05:14,680
13, of course, gets a
little bit more interesting.

90
00:05:14,680 --> 00:05:18,010
Once we get past single digits,
of course, what we have to do

91
00:05:18,010 --> 00:05:20,530
is use a slightly
different conversion chart.

92
00:05:20,530 --> 00:05:30,550
So what we have are the values
of 10, 11, 12, 13, 14, and 15.

93
00:05:30,550 --> 00:05:32,680
And these, of course,
are going to convert

94
00:05:32,680 --> 00:05:41,470
to A, B, C, D, E, and F.

95
00:05:41,470 --> 00:05:45,850
So in this case, since
we're talking about a 13,

96
00:05:45,850 --> 00:05:48,340
it's going to be this
entry right here.

97
00:05:48,340 --> 00:05:51,670
And that means that our final
answer for our conversion

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00:05:51,670 --> 00:05:54,580
is going to be D9.

99
00:05:54,580 --> 00:06:00,040
So what we see is this
value that's 217 in decimal

100
00:06:00,040 --> 00:06:03,820
is D9 in hex.

101
00:06:03,820 --> 00:06:06,820
The big thing to remember
with hexadecimal, when you're

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00:06:06,820 --> 00:06:08,950
going to convert
it back to binary,

103
00:06:08,950 --> 00:06:12,550
is you want to treat the two
digits separately and then

104
00:06:12,550 --> 00:06:15,430
remember to convert them
on the scale of dealing

105
00:06:15,430 --> 00:06:18,040
with four bits at a
time meaning we're only

106
00:06:18,040 --> 00:06:24,250
going to be dealing with the
values of 1, 2, 4, and 8.

107
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So now let's talk about
how we use this hexadecimal

108
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in our addressing.

109
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So a couple of things
to keep in mind.

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First is, of course, IPv6
addresses are 128 bits.

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So this makes them exponentially
larger than the 32 bits

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we have in IPv4.

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This is a very
very large number.

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We split this up when we're
entering it into devices

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into 816-bit hex fields.

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00:06:55,240 --> 00:06:59,470
These hex fields will
be separated by a colon.

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So for example, we could have
something like DB8:100:13:4

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and so on.

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00:07:11,200 --> 00:07:16,060
The important thing here
is these addresses can be

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00:07:16,060 --> 00:07:20,770
and in fact will be by the
devices themselves shortened.

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00:07:20,770 --> 00:07:24,100
Now, we have some rules
for shortening these.

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First, any consecutive
zeros can be eliminated.

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But we can only do this once.

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This is done with double
colons in the address.

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So for example, I could say
2001::1 could be a valid IPv6

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00:07:47,980 --> 00:07:49,240
address.

127
00:07:49,240 --> 00:07:55,900
I'm eliminating a ton of zeros
between these two colons.

128
00:07:55,900 --> 00:07:58,900
The way this works
is the devices

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00:07:58,900 --> 00:08:02,440
will split the address
right between the colons,

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00:08:02,440 --> 00:08:06,190
move the front part to
the left of the field,

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00:08:06,190 --> 00:08:09,280
move the right section to
the right side of the field,

132
00:08:09,280 --> 00:08:13,900
and fill in x number
of zeros however

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many zeroes it takes
to make this 128 bits.

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00:08:19,280 --> 00:08:21,800
So you could
eliminate two fields

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00:08:21,800 --> 00:08:24,320
of zeros, four fields of zeros.

136
00:08:24,320 --> 00:08:28,730
In this example, I eliminated
six fields of zeros.

137
00:08:28,730 --> 00:08:31,460
The other rule for
shortening these addresses

138
00:08:31,460 --> 00:08:38,360
is that leading zeros can be
eliminated in any given field.

139
00:08:38,360 --> 00:08:40,700
Now, this one you
might have noticed,

140
00:08:40,700 --> 00:08:43,880
I do just out of habit.

141
00:08:43,880 --> 00:08:47,720
I already did it numerous
times on our examples here.

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00:08:47,720 --> 00:08:50,330
There should have been
a zero in front of this,

143
00:08:50,330 --> 00:08:52,790
there should have been
a zero right here,

144
00:08:52,790 --> 00:08:55,040
there should have been
two zeros in here,

145
00:08:55,040 --> 00:08:57,320
there should have been
three zeros in here.

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00:08:57,320 --> 00:09:00,770
So I already did it when I was
just writing out the numbers.

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00:09:00,770 --> 00:09:03,740
There should have been three
zeros over here as well,

148
00:09:03,740 --> 00:09:07,640
but I just eliminated them
because there's no difference.

149
00:09:07,640 --> 00:09:09,200
And if you think
about it in terms

150
00:09:09,200 --> 00:09:11,510
of something say
like your paycheck,

151
00:09:11,510 --> 00:09:14,358
if your paycheck
is going to be--

152
00:09:14,358 --> 00:09:15,650
we'll just make this real easy.

153
00:09:15,650 --> 00:09:19,070
Let's say your paycheck
is $1000, well,

154
00:09:19,070 --> 00:09:22,970
you're not going to really
care if instead of $1,000

155
00:09:22,970 --> 00:09:29,120
your company gives you 001000.

156
00:09:29,120 --> 00:09:32,120
You wouldn't really care
if your paycheck said this,

157
00:09:32,120 --> 00:09:33,830
because that's still 1000.

158
00:09:33,830 --> 00:09:35,630
When you go to
deposit your check

159
00:09:35,630 --> 00:09:37,298
or in the bank looks
at this they're

160
00:09:37,298 --> 00:09:39,590
going to go oh, yeah, well,
that's interesting and all.

161
00:09:39,590 --> 00:09:41,630
But yeah, we don't
care about that.

162
00:09:41,630 --> 00:09:43,490
That doesn't change the value.

163
00:09:43,490 --> 00:09:47,840
However, you might care
a whole lot at least

164
00:09:47,840 --> 00:09:52,940
I probably would if instead
they eliminated trailing zeros

165
00:09:52,940 --> 00:09:56,330
and instead gave you $10.

166
00:09:56,330 --> 00:09:59,300
I'm sure like me you would be
sitting there going, excuse me,

167
00:09:59,300 --> 00:10:01,670
where are the rest of my digits.

168
00:10:01,670 --> 00:10:04,670
The bank might be OK
with this, your company

169
00:10:04,670 --> 00:10:06,500
may be OK with
this, I'm guessing

170
00:10:06,500 --> 00:10:07,820
you probably wouldn't be.

171
00:10:07,820 --> 00:10:09,710
So what I'm trying
to point out here,

172
00:10:09,710 --> 00:10:13,370
of course, is that leading
zeros really don't mean anything

173
00:10:13,370 --> 00:10:16,850
but trailing zeros are critical.

174
00:10:16,850 --> 00:10:18,560
You see if we look at
this field right up

175
00:10:18,560 --> 00:10:21,950
here as an example,
that's supposed to be 100,

176
00:10:21,950 --> 00:10:24,500
or we could say 100.

177
00:10:24,500 --> 00:10:27,140
Well, if I eliminated
trailing zeros,

178
00:10:27,140 --> 00:10:31,550
it would become a 10 or
maybe just a 1 by itself.

179
00:10:31,550 --> 00:10:35,120
Leading zeros don't matter,
trailing zeros matter a lot.

180
00:10:35,120 --> 00:10:39,800
We can only eliminate
leading zeros in a field.

181
00:10:39,800 --> 00:10:45,080
But, again, those can be
eliminated with no problems.

182
00:10:45,080 --> 00:10:47,750
So let's look at
this other example.

183
00:10:47,750 --> 00:10:51,620
If we look at our
rules here, the 2001

184
00:10:51,620 --> 00:10:57,920
would have to stay a 2001, then
we could eliminate this zero.

185
00:10:57,920 --> 00:11:00,950
So this would become DB8.

186
00:11:00,950 --> 00:11:03,320
We could eliminate this zero.

187
00:11:03,320 --> 00:11:06,140
So, again, this
would become 100.

188
00:11:06,140 --> 00:11:10,190
Then we could eliminate
this field, this field,

189
00:11:10,190 --> 00:11:14,870
and this field just by
doing double colons.

190
00:11:14,870 --> 00:11:19,970
We could drop this zero
and make this just 118.

191
00:11:19,970 --> 00:11:24,080
And, of course, the last one
we can drop these three fields

192
00:11:24,080 --> 00:11:26,750
and just make it a 1.

193
00:11:26,750 --> 00:11:31,850
So that's the proper way
to shorten an IPv6 address.

194
00:11:31,850 --> 00:11:34,700
Now, something else
to discuss about IPv6

195
00:11:34,700 --> 00:11:37,730
addressing is a new
type of addressing

196
00:11:37,730 --> 00:11:43,340
that we have in IPv6 called
Link Local Addresses.

197
00:11:43,340 --> 00:11:47,000
Now, there's some special
things about these addresses.

198
00:11:47,000 --> 00:11:50,540
First, they are from a given
known range of addresses.

199
00:11:50,540 --> 00:11:57,290
So they're all from the
FE80/10 address range.

200
00:11:57,290 --> 00:12:00,860
Also, since they
are linked local,

201
00:12:00,860 --> 00:12:03,830
they are not
ratable, that's what

202
00:12:03,830 --> 00:12:07,760
the word local is implying
that this traffic can't

203
00:12:07,760 --> 00:12:09,650
leave this segment.

204
00:12:09,650 --> 00:12:12,020
Now, that brings up an
interesting side effect

205
00:12:12,020 --> 00:12:15,680
on our devices which can
actually be quite useful.

206
00:12:15,680 --> 00:12:18,920
Since they're not
routable well, that

207
00:12:18,920 --> 00:12:24,560
means that all of the interfaces
on a router can be the same.

208
00:12:24,560 --> 00:12:27,440
Meaning use the same address.

209
00:12:27,440 --> 00:12:29,630
So if I had a
router, for example,

210
00:12:29,630 --> 00:12:31,760
and I had we'll
just make it easy,

211
00:12:31,760 --> 00:12:35,180
we'll just have three
interfaces off of it,

212
00:12:35,180 --> 00:12:40,430
that means that I can have the
address on this interface be

213
00:12:40,430 --> 00:12:41,306
FE80::1.

214
00:12:41,306 --> 00:12:44,720

215
00:12:44,720 --> 00:12:47,854
This interface could be FE80::1.

216
00:12:47,854 --> 00:12:51,290

217
00:12:51,290 --> 00:12:54,290
And this one could be FE80::1.

218
00:12:54,290 --> 00:12:57,140

219
00:12:57,140 --> 00:13:00,500
And this can be very handy
particularly if this is say,

220
00:13:00,500 --> 00:13:03,500
router one because
we can use this then

221
00:13:03,500 --> 00:13:05,630
to identify the device.

222
00:13:05,630 --> 00:13:07,580
Now, of course, if
there's a router

223
00:13:07,580 --> 00:13:10,850
on the other end of this
circuit, any of these cables

224
00:13:10,850 --> 00:13:13,280
it would have to have
a different address.

225
00:13:13,280 --> 00:13:16,600
That's what we're saying with
this fourth point over here

226
00:13:16,600 --> 00:13:21,670
that addresses on the
same link must be unique.

227
00:13:21,670 --> 00:13:24,760
So that means that I could not
put another router down here

228
00:13:24,760 --> 00:13:32,410
and try to give it the address
FE80::1 because that would be

229
00:13:32,410 --> 00:13:34,210
on the same segment.

230
00:13:34,210 --> 00:13:35,920
So in order for
this to be valid,

231
00:13:35,920 --> 00:13:38,110
I would have to make
it a two or well,

232
00:13:38,110 --> 00:13:41,380
anything else, anything
other than a one.

233
00:13:41,380 --> 00:13:43,300
Also, this is a quick note.

234
00:13:43,300 --> 00:13:48,070
Our iOS XE devices do
support something called IPv6

235
00:13:48,070 --> 00:13:50,500
scoped address architecture.

236
00:13:50,500 --> 00:13:54,430
This is referenced in RFC 4007.

237
00:13:54,430 --> 00:13:56,860
It's not a very
popular implementation.

238
00:13:56,860 --> 00:14:01,000
I would just be aware
that iOS XE supports it.

239
00:14:01,000 --> 00:14:04,840
And finally, as we mentioned
during the introduction,

240
00:14:04,840 --> 00:14:09,340
IPv6 does not support ARP,
which is address resolution

241
00:14:09,340 --> 00:14:14,650
protocol used by IPv4,
rather we use something

242
00:14:14,650 --> 00:14:16,780
called neighbor discovery.

243
00:14:16,780 --> 00:14:21,910
The job here is still to do
layer 3 to layer 2 address

244
00:14:21,910 --> 00:14:23,290
translation.

245
00:14:23,290 --> 00:14:28,330
However, this is
now part of ICMPv6.

246
00:14:28,330 --> 00:14:30,730
Depending how well
you remember IPv4,

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you may remember
that ARP was actually

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a completely separate protocol.

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It's not part of the IP stack.

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With IPv6 it is.

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It's been moved into ICMP.

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Now, for neighbor discovery, it
uses a type 135 ICMP message.

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For the neighbor
advertisement, which

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is essentially the answer to
the request, this uses type 136.

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Something else that's built
into neighbor discovery that's

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a little bit unique
to IPv6 is something

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called a router advertisement.

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Routers actually
advertise themselves

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onto the network in IPv6.

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Again, this is essentially
part of neighbor discovery.

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It's also part of
ICMP version 6.

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But this uses type 134.

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So we'll see some
of this stuff in use

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as we move through the rest
of the videos in this skill.

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In this video, we
jumped in and got what

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I'm hoping is a review on IPv6.

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So we started off
by looking at how

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to do some address conversions
from decimal to hex and hex

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to binary, and all
that fun stuff.

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And then we took a look at
the IPv6 addresses themselves.

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How to shorten them properly,
we talked a little bit

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about link local addressing.

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And then, of course,
we wrapped up here

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with our discussion
of neighbor discovery

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which is what we use
in IPv6 instead of ARP.

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I hope this has been
informative for you

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and I'd like to thank
you for viewing.

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