IPv6 Addressing
Global Unicast Address
■ generate a link-local address on the VLAN as described in the preceding
section (page 3-13).
■ transmit a router solicitation on the VLAN, and to listen for advertise-
ments from any IPv6 routers on the VLAN.
For each unique router advertisement (RA) the switch receives from any
router(s), the switch configures a unique, global unicast address. This address
type is composed of a 64-bit network prefix specified by the router advertise-
ment, plus a device identifier generated in the same way as described in the
preceding section for link-local addresses (using the EUI algorithm). For
example, suppose the following is true:
■ IPv6 is not enabled on VLAN 1.
■ The MAC address for VLAN 1 is 00-15-60-7a-ad-c0.
■ A router on the same VLAN transmits router advertisements that assign
the prefix 2001:0:260:212/64, plus a 64-bit interface identifier generated
using the EUI format.
In this case, enabling IPv6 address autoconfiguration on VLAN 1 generates the
following address assignments on VLAN 1:
■ link-local unicast: fe80::215:60ff:fe7a:adc0/64
■ global unicast:2001:0:260:212:215:60ff:fe7a:adc0/64
IPv6 Already Enabled. Enabling address autoconfiguration on a VLAN
when IPv6 is already enabled on the VLAN creates a global unicast address in
the same way as described above, except that the device identifier applied to
the new global address is a duplicate of the 64-bit identifier in the current link-
local address.
Note After a global unicast address has been configured, its device identifier will
not be changed by any later changes to the link-local address.
Static Configuration of a Global Unicast Address
A global unicast address can be configured statically on a VLAN interface. If
IPv6 is not already enabled on a VLAN, then statically configuring a global
unicast address automatically generates a link-local unicast address on the
VLAN, as described in the preceding section. To statically configure a global
unicast address, refer to “Statically Configuring A Global Unicast Address” on
page 4-13.
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