IPv6 Addressing Configuration
Duplicate Address Detection (DAD)
that includes its link-local address. If the newly configured address is from a
static or DHCPv6 source and is found to be a duplicate, it is labelled as
duplicate in the “Address Status” field of the show ipv6 command, and is not
used. If an autoconfigured address is found to be a duplicate, it is dropped and
the following message appears in the Event Log:
W < date > < time > 00019 ip: ip address < IPv6-address >
removed from vlan id < vid >
DAD does not perform periodic checks of existing addresses. However, when
a VLAN comes up with IPv6 unicast addresses configured (as can occur during
a reboot) the switch runs DAD for each address on the interface by sending
neighbor solicitations to the All-Nodes multicast address as described above.
If an address is configured while DAD is disabled, the address is assumed to
be unique and is assigned to the interface. If you want to verify the uniqueness
of an address configured while DAD was disabled, re-enable DAD and then
either delete and reconfigure the address, or reboot the switch.
Configuring DAD
Syntax: ipv6 nd dad-attempts < 0 - 600 >
This command is executed at the global config level, and
configures the number of neighbor solicitations to send when
performing duplicate address detection for a unicast address
configured on a VLAN interface.
< 0 - 600 >: The number of consecutive neighbor solicitation
messages sent for DAD inquiries on an interface. Setting this
value to 0 disables DAD on the interface. Disabling DAD
bypasses checks for uniqueness on newly configured
addresses. If a reboot is performed while DAD is disabled, the
duplicate address check is not performed on any IPv6
addresses configured on the switch.
Default: 3 (enabled); Range: 0 - 600 (0 = disabled)
The no form of the command restores the default setting (3).
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