GS3700/XGS3700 Series User’s Guide
404
A
P P E N D I X
B
IPv6
Overview
IPv6 (Internet Protocol version 6), is designed to enhance IP address size and features. The
increase in IPv6 address size to 128 bits (from the 32-bit IPv4 address) allows up to 3.4 x 10
38
IP
addresses.
IPv6 Addressing
The 128-bit IPv6 address is written as eight 16-bit hexadecimal blocks separated by colons (:). This
is an example IPv6 address
2001:0db8:1a2b:0015:0000:0000:1a2f:0000
.
IPv6 addresses can be abbreviated in two ways:
• Leading zeros in a block can be omitted. So
2001:0db8:1a2b:0015:0000:0000:1a2f:0000
can
be written as
2001:db8:1a2b:15:0:0:1a2f:0
.
• Any number of consecutive blocks of zeros can be replaced by a double colon. A double colon can
only appear once in an IPv6 address. So
2001:0db8:0000:0000:1a2f:0000:0000:0015
can be
written as
2001:0db8::1a2f:0000:0000:0015
,
2001:0db8:0000:0000:1a2f::0015
,
2001:db8::1a2f:0:0:15
or
2001:db8:0:0:1a2f::15
.
Prefix and Prefix Length
Similar to an IPv4 subnet mask, IPv6 uses an address prefix to represent the network address. An
IPv6 prefix length specifies how many most significant bits (start from the left) in the address
compose the network address. The prefix length is written as “/x” where x is a number. For
example,
2001:db8:1a2b:15::1a2f:0/32
means that the first 32 bits (
2001:db8
) is the subnet prefix.
Link-local Address
A link-local address uniquely identifies a device on the local network (the LAN). It is similar to a
“private IP address” in IPv4. You can have the same link-local address on multiple interfaces on a
device. A link-local unicast address has a predefined prefix of fe80::/10. The link-local unicast
address format is as follows.
Table 216
Link-local Unicast Address Format
1111 1110 10
0
Interface ID
10 bits
54 bits
64 bits
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
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71
72
73
74
75
76
77
78
79
80
81
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83
84
85
86
87
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90
91
92
93
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95
96
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99
100
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102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
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148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
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165
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168
169
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171
172
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177
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