Chapter 33 IPv6 Commands
Ethernet Switch CLI Reference Guide
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33.1.2 IPv6 Terms
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.
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.
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 82 Link-local Unicast Address Format
Global Address
A global address uniquely identifies a device on the Internet. It is similar to a “public IP
address” in IPv4. The global address format as follows.
Table 83 Global Address Format
The global ID is the network identifier or prefix of the address and is used for routing. This
may be assigned by service providers.
The subnet ID is a number that identifies the subnet of a site.
Multicast Addresse
In IPv6, multicast addresses provide the same functionality as IPv4 broadcast addresses.
Broadcasting is not supported in IPv6. A multicast address allows a host to send packets to all
hosts in a multicast group.
1111 1110 10 0 Interface ID
10 bits 54 bits 64 bits
001 Global ID Subnet ID Interface ID
3 bits 45 bits 16 bits 64 bits
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