Extreme Networks ExtremeWare XOS Guide Manual page 517

Overview of IPv6 Unicast Routing
Leading zeros in a four-digit group can be omitted. There is a special use of a double colon (::) in an
address. The double colon stands for one or more groups of 16 bits of zeros and can only be used once
in an address. For example, the following addresses:
fe80:0:0:0:af34:2345:4afe:0
fe80:0:0:111:0:0:0:fe11
3c12:0:0:0:0:89:ff:3415
can be represented as:
fe80::af34:2345:4afe:0
fe80:0:0:111::fe11
3c12::89:ff:3415
Additionally, you can specify an address in a mixed IPv4/IPv6 mode that uses six, four-digit
hexadecimal numbers for the highest-order part of the address, and uses the IPv4 dotted decimal
representation for the lowest-order remaining portion. For example:
0:0:0:0:0:0:192.168.1.1
0:0:0:0:0:ffff:10.0.14.254
These can be represented as:
::192.168.1.1
::ffff:10.0.14.254
Duplicate Address Detection
When you configure an active interface with an IPv6 address, the interface must send out an
advertisement containing its address. All other interfaces on the subnet have the opportunity to respond
to the newly configured interface, and inform it that the address is a duplicate. Only after this process
occurs, can the interface use the newly configured address. If the interface receives a message that the
newly configured address is a duplicate, it cannot use the address.
Until the Duplicate Address Detection (DAD) process completes, the new address is considered
tentative, and will be shown as such in any display output. If the address is a duplicate, it will also be
labeled as such, and must be reconfigured. On an active interface, the DAD process should occur so
quickly that you would not see the address labeled as tentative. However, if you are configuring an
interface before enabling it, and you display the configuration, you will see that the address is currently
tentative. As soon as you enable the interface, the address should be ready to use, or labeled as
duplicate and must be reconfigured.
See RFC 2462, IPv6 Stateless Address Autoconfiguration, for more details.
Scoped Addresses
IPv6 uses a category of addresses called link local addresses that are used solely on a local subnet. Due
to the way that local link addresses can be automatically assigned, a switch can have the same link local
address assigned to different VLANs, or different neighbors on different links may be using the same
link local address. Because of this, there are cases where you need to specify an address and a VLAN/
tunnel to indicate which interface to use. For those cases, you can indicate the interface by using a
scoped address. To scope the address, append the VLAN/tunnel name to the end of the address,
separated by a percent sign (%). For example, to indicate the link local address fe80::2 on VLAN finance,
use the following form:
fe80::14%finance
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ExtremeWare XOS 11.3 Concepts Guide