Cisco 300 Series Cli Manual page 733

IPv6 Router Commands
78-21075-01 Command Line Interface Reference Guide
remain in a tentative state while duplicate address detection is performed).
Duplicate address detection uses neighbor solicitation messages to verify the
uniqueness of Unicast IPv6 addresses.
The DupAddrDetectTransmits node configuration variable (as specified in RFC
4862, IPv6 Stateless Address Autoconfiguration) is used to automatically
determine the number of consecutive neighbor solicitation messages that are sent
on an interface, while duplicate address detection is performed on a tentative
Unicast IPv6 address.
The interval between duplicate address detection, neighbor solicitation messages
(the duplicate address detection timeout interval) is specified by the neighbor
discovery-related variable RetransTimer (as specified in RFC 4861, Neighbor
Discovery for IPv6), which is used to determine the time between retransmissions
of neighbor solicitation messages to a neighbor when resolving the address or
when probing the reachability of a neighbor. This is the same management
variable used to specify the interval for neighbor solicitation messages during
address resolution and neighbor unreachability detection. Use the ipv6 nd
ns-interval command to configure the interval between neighbor solicitation
messages that are sent during duplicate address detection.
Duplicate address detection is suspended on interfaces that are administratively
down. While an interface is administratively down, the Unicast IPv6 addresses
assigned to the interface are set to a pending state. Duplicate address detection is
automatically restarted on an interface when the interface returns to being
administratively up.
An interface returning to administratively up, restarts duplicate address detection
for all of the Unicast IPv6 addresses on the interface. While duplicate address
detection is performed on the link-local address of an interface, the state for the
other IPv6 addresses is still set to TENTATIVE. When duplicate address detection
is completed on the link-local address, duplicate address detection is performed
on the remaining IPv6 addresses.
When duplicate address detection identifies a duplicate address, the state of the
address is set to DUPLICATE and the address is not used. If the duplicate address
is the link-local address of the interface, the processing of IPv6 packets is
disabled on the interface and an error SYSLOG message is issued.
If the duplicate address is a global address of the interface, the address is not
used and an error SYSLOG message is issued.
All configuration commands associated with the duplicate address remain as
configured while the state of the address is set to DUPLICATE.
If the link-local address for an interface changes, duplicate address detection is
performed on the new link-local address and all of the other IPv6 address
associated with the interface are regenerated (duplicate address detection is
performed only on the new link-local address).
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