Duplicate Address Detection
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... site-local and global addresses via stateless address
autoconfiguration, and the Duplicate Address Detection procedure. The
details of autoconfiguration using the stateful protocol are
...
... addresses before assigning them to an interface. The Duplicate
Address Detection algorithm is performed on all addresses,
...
... stateless or stateful
autoconfiguration. This document defines the Duplicate Address
Detection algorithm.
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... document. In addition, routers are expected to successfully pass the
Duplicate Address Detection procedure described in this document on
all addresses prior to assigning them to an interface ...
... tentative address, but accepts Neighbor Discovery packets
related to Duplicate Address Detection for the tentative
address.
...
... stateful address
autoconfiguration should be tested for uniqueness individually. To
accommodate sites that believe the overhead of performing Duplicate
Address Detection outweighs its benefits, the use of Duplicate
Address Detection can be disabled through the administrative setting
of a per-interface ...
... accommodate sites that believe the overhead of performing Duplicate
Address Detection outweighs its benefits, the use of Duplicate
Address Detection can be disabled through the administrative setting
of a per-interface configuration flag.
...
... link-local address using the
procedure outlined below. In addition, routers perform Duplicate
Address Detection on all addresses prior to assigning them to an
interface ...
... The number of consecutive Neighbor Solicitation
messages sent while performing Duplicate Address
Detection on a tentative address. A value of zero
indicates that Duplicate Address Detection ...
... Duplicate Address
Detection on a tentative address. A value of zero
indicates that Duplicate Address Detection is not
performed on tentative addresses. A value of one
...
... specifies the delay between consecutive Neighbor
Solicitation transmissions performed during
Duplicate Address Detection (if
DupAddrDetectTransmits is greater than 1), as well
as the time a node ...
... node waits after sending the last
Neighbor Solicitation before ending the Duplicate
Address Detection process.
...
...
Beyond the formation of a link-local address and using Duplicate
Address Detection, how routers (auto)configure their interfaces is
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... Duplicate Address Detection ...
...
Duplicate Address Detection is performed on unicast addresses prior
to assigning them to an interface ...
... to assigning them to an interface whose DupAddrDetectTransmits
variable is greater than zero. Duplicate Address Detection MUST take
place on all unicast addresses, regardless of whether they are
...
... Duplicate Address Detection MUST NOT be performed on anycast
addresses.
...
... uniqueness, and if no duplicate address is detected, an
implementation MAY choose to skip Duplicate Address Detection
for additional addresses derived from the same interface
identifier ...
... addresses will still exist (e.g., if the link was partitioned while
Duplicate Address Detection was performed).
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...
An address on which the duplicate Address Detection Procedure is
applied is said to be tentative until the procedure has completed
successfully. A tentative address ...
...
It should also be noted that Duplicate Address Detection must be
performed prior to assigning an address to an interface ...
... If a node begins using an address in parallel with Duplicate Address
Detection, and another node is already using the address, the node ...
... address, the node
performing Duplicate Address Detection will erroneously process
traffic intended for the other node ...
... address at the same time. In order to improve the robustness of the
Duplicate Address Detection algorithm, an interface MUST receive and
...
... address, the solicitation is from a node performing Duplicate Address
Detection. If the solicitation is from another node, the tentative
address is a duplicate and should not be used (by either node ...
... multicast packets.
The details of how such a facility is implemented may prevent
Duplicate Address Detection from working correctly. See the Appendix
for further discussion.
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... tentative address is a
duplicate. This condition occurs when two nodes run Duplicate
Address Detection simultaneously, but transmit initial
solicitations at different times (e.g., by selecting different
random delay values before transmitting ...
... tentative address is a
duplicate. This condition occurs when two nodes run Duplicate
Address Detection simultaneously and transmit solicitations at
roughly the same time.
...
... When Duplicate Address Detection Fails ...
...
The use of Duplicate Address Detection opens up the possibility of
denial of service attacks. Any node ...
... APPENDIX A: LOOPBACK SUPPRESSION & DUPLICATE ADDRESS DETECTION ...
... roughly the same time (e.g., Neighbor Solicitations for a tentative
address as part of Duplicate Address Detection messages). Although a
receiver will receive both packets, it cannot determine which packet
...
... hardware itself suppresses
loopbacks, a node running Duplicate Address Detection simply counts
the number of Neighbor Solicitations received for a tentative address ...
... same link-layer address. Duplicate Address
Detection will fail on interfaces that filter received packets in
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... If a node performing Duplicate Address Detection discards
received packets having the same source link-layer address as
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... Neighbor
Advertisement and Neighbor Solicitation messages required to
make Duplicate Address Detection work correctly. This
particular problem can be avoided by temporarily disabling the
software suppression of loopbacks while a node ...
... software suppression of loopbacks while a node performs
Duplicate Address Detection.
...
... source address as
the interface, it will also discard Duplicate Address
Detection-related Neighbor Solicitation messages sent by another
node ...
... layer address. Consequently,
Duplicate Address Detection will fail, and the other node will
configure a non-unique address ...
... address. Since it is generally impossible
to know when another node is performing Duplicate Address
Detection, this scenario can be avoided only if software
suppression of loopback is permanently disabled.
...
...
Thus, to perform Duplicate Address Detection correctly in the case
where two interfaces are using the same link ...