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Chapter 5 Broadband
FMG3024-D10A / FMG3025-D10A Series User’s Guide
69
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.
DHCPv6
The Dynamic Host Configuration Protocol for IPv6 (DHCPv6, RFC 3315) is a server-client protocol
that allows a DHCP server to assign and pass IPv6 network addresses, prefixes and other
configuration information to DHCP clients. DHCPv6 servers and clients exchange DHCP messages
using UDP.
Each DHCP client and server has a unique DHCP Unique IDentifier (DUID), which is used for
identification when they are exchanging DHCPv6 messages. The DUID is generated from the MAC
address, time, vendor assigned ID and/or the vendor's private enterprise number registered with
the IANA. It should not change over time even after you reboot the device.
IPv6 6to4 Mode
This mode also enables the Device to convert IPv6 packets to IPv4 packets. But instead of pre-
configuring the destination router, you need to configure a 6to4 relay router that helps to route the
packets to any IPv6 networks.
In this mode, the Device should get a public IPv4 address for the WAN. The Device adds an IPv4
header to an IPv6 packet when transmitting the packet to the Internet. In reverse, the Device
removes the IPv4 header from an IPv6 packet when receiving it from the Internet.