IPv6 Addressing
Global Unicast Address
Global Unicast AddressA global unicast address is required for unicast traffic to be routed across VLANs within an organization as well as across the public internet. To support subnetting, a VLAN can be configured with multiple global unicast addresses. Any of the following methods can be used to configure this kind of address on a VLAN:
■stateless address autoconfiguration using a prefix received in an adver tisement received from a router on the VLAN (page
■stateful address configuration using DHCPv6 (page
■static address configuration (page
Stateless Autoconfiguration of a Global Unicast
Address
If there is an
Router Advertisements. With autoconfiguration enabled, if the switch receives the same prefix from router advertisements (RAs) from multiple IPv6 routers on the same VLAN, then one global unicast address is configured with that prefix. If different prefixes are received from different routers on the same VLAN, then there will be one address configured on the VLAN for each unique prefix received. Where there are multiple routers on the VLAN, the default route for the VLAN is determined by the relative router priorities included in the RAs the VLAN receives. If the highest priority is duplicated on multiple routers, then the first RA detected on the VLAN determines the default route.
If the RA used to define the prefix for an autoconfigured address ceases to be received on the VLAN, then the address becomes deprecated. (Refer to “IPv6 Address Deprecation” on page
If IPv6 is not already enabled on a VLAN when you enable autoconfiguration on the VLAN, then the switch automatically generates a
If IPv6 Is Not Already Enabled. Enabling address autoconfiguration on a VLAN when IPv6 is not already enabled on the VLAN causes the switch to: