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.

 

 

N o t e

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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