Table of Contents
Advertisement
• 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.
8.6.2 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.
8.6.3 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.
The first 48 bits of the IPv6 subnet mask are for Internet routing or fixed for local address, the 49th
to the 54th bits are for subnetting and the last 64 bits are for interface identifying. The 16 binary
digits for subnetting allows an organization to set up to 65,535 individual subnets.
8.6.4 Interface ID
In IPv6, an interface ID is a 64-bit identifier. It identifies a physical interface (for example, an
Ethernet port) or a virtual interface (for example, the management IP address for a VLAN). One
interface should have a unique interface ID.
8.6.5 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 13 Link-local Unicast Address Format
1111 1110 10
10 bits
8.6.6 Global Address
A global address uniquely identifies a device on the Internet. It is similar to a "public IP address" in
IPv4. A global unicast address starts with a 2 or 3. The global address format as follows.
VES1724-56 User's Guide
0
Interface ID
54 bits
64 bits
Chapter 8 Basic Setting
77
Hide quick links:
Advertisement
Table of Contents
