VMG1312-B Series User’s Guide 351
APPENDIX E
IPv6
Overview
I Pv6 ( I nternet Prot ocol version 6) , is designed t o enhance I P address size and feat ures. The
increase in I Pv6 address size t o 128 bit s ( from the 32-bit I Pv4 address) allow s up t o 3.4 x 10
38
I P
addresses.
IPv6 Addressing
The 128- bit I Pv6 address is writ t en as eight 16- bit hexadecim al blocks separated by colons ( : ) . This
is an exam ple I Pv6 address 2001:0db8:1a2b:0015:0000:0000:1a2f:0000.
I Pv6 addresses can be abbreviat ed in t wo ways:
• Leading zeros in a block can be om it ted. So 2001:0db8:1a2b:0015:0000:0000:1a2f:0000 can
be writt en as 2001:db8:1a2b:15:0:0:1a2f:0.
• Any num ber of consecutive blocks of zeros can be replaced by a double colon. A double colon can
only appear once in an I Pv6 address. So 2001:0db8:0000:0000:1a2f:0000:0000:0015 can be
writ t en 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
Sim ilar t o an I Pv4 subnet m ask, I Pv6 uses an address prefix t o represent the network address. An
I Pv6 prefix length specifies how m any m ost significant bit s ( start from t he left) in the address
com pose t he net work address. The prefix lengt h is writt en as “ / x” where x is a num ber. For
exam ple,
2001:db8:1a2b:15::1a2f:0/32
m eans t hat the first 32 bits ( 2001:db8) is the subnet prefix.
Link-local Address
A link- local address uniquely identifies a device on t he local net work (t he LAN) . I t is sim ilar t o a
“ private I P address” in I Pv4. You can have t he sam e link- local address on m ult iple interfaces on a
device. A link- local unicast address has a predefined prefix of fe80: : / 10. The link-local unicast
address form at is as follows.
Table 126 Link-local Unicast Address Form at
1111 1110 10 0 I nterface I D
10 bit s 54 bit s 64 bit s
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