ZyXEL Communications PMG2006-T20A User Manual page 40

IPv6 Introduction
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
PMG2006-T20A can use IPv4/IPv6 dual stack to connect to IPv4 and IPv6 networks, and supports IPv6
rapid deployment (6RD).
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.
IPv6 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.
IPv6 Subnet Masking
Both an IPv6 address and IPv6 subnet mask compose of 128-bit binary digits, which are divided into
eight 16-bit blocks and written in hexadecimal notation. Hexadecimal uses four bits for each character
(1 ~ 10, A ~ F). Each block's 16 bits are then represented by four hexadecimal characters. For example,
FFFF:FFFF:FFFF:FFFF:FC00:0000:0000:0000.
IPv6 Rapid Deployment
Use IPv6 Rapid Deployment (6rd) when the local network uses IPv6 and the ISP has an IPv4 network.
When the PMG2006-T20A has an IPv4 WAN address and you set IPv4/IPv6 Mode to IPv4 Only, you can
enable 6rd to encapsulate IPv6 packets in IPv4 packets to cross the ISP's IPv4 network.
The PMG2006-T20A generates a global IPv6 prefix from its IPv4 WAN address and tunnels IPv6 traffic to
the ISP's Border Relay router (BR in the figure) to connect to the native IPv6 Internet. The local network
can also use IPv4 services. The PMG2006-T20A uses it's configured IPv4 WAN IP to route IPv4 traffic to the
IPv4 Internet.
Chapter 6 Broadband
PMG2006-T20A User's Guide
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IP addresses. The