KB.15.15

Enabling autoconfiguration of a global unicast address and a default router

identity on a VLAN

Enabling autoconfig or rebooting the switch with autoconfig enabled on a VLAN causes the switch

to configure IPv6 addressing on the VLAN using RAs and an EUI-64 interface identifier.

Syntax:

[no] ipv6 address autoconfig

Implements unicast address autoconfiguration as follows:

• If IPv6 is not already enabled on the VLAN, enables IPv6 and generates a

link-local ( EUI-64) address.

• Generates router solicitations (RSs) on the VLAN.

• If an RA is received on the VLAN, the switch uses the route prefix in the RA to

configure a global unicast address. The interface identifier for this address is

the same as the interface identifier used in the current link-local address at the

time the RA is received. This can be either a statically configured or the

(automatic) EUI-64 interface identifier, depending on how the link-local address

was configured.

If an RA is not received on the VLAN after autoconfig is enabled, a link-local

address is present, but no global unicast addresses are autoconfigured.

NOTE: If a link-local address is already configured on the VLAN, a later,

autoconfigured global unicast address, uses the same interface identifier as

the link-local address.

Autoconfigured and DHCPv6-assigned global unicast addresses with the same

prefix are mutually exclusive on a VLAN. On a given switch, if both options

are configured on the same VLAN, only the first to acquire a global unicast

address is used.

After verification of uniqueness by DAD, an IPv6 address assigned to a VLAN by

autoconfiguration is set to the preferred and valid lifetimes specified by the RA used

to generate the address and is configured as a preferred address.

Default: Disabled.

The no form of the command produces different results, depending on how IPv6 is

configured on the VLAN: If IPv6 was enabled only by the autoconfig command,

deleting this command disables IPv6 on the VLAN.

Viewing current IPv6 autoconfiguration settings

To view the current IPv6 autoconfiguration settings per-VLAN or per-tunnel, use show run.

To view all currently configured IPv6 unicast addresses, use the following:

• show ipv6

Lists IPv6 addresses for all VLANs configured on the switch.

• show ipv6 vlan vid

Lists IPv6 addresses configured on the VLAN.

• show ipv6 tunnel tunnel

Lists IPv6 addresses configured on the tunnel.

14 IPv6 Addressing Configuration