To configure the number of consecutive neighbor solicitation messages that are sent on an interface while duplicate address
detection is performed on the unicast IPv6 addresses of the interface, use the
ipv6
nd
dad
attempts command in interface configuration mode. To return the number of messages to the default value, use the
no form of this command.
ipv6 nd dad attempts value
no ipv6 nd dad attempts value
Syntax Description
value
|
The number of neighbor solicitation messages. The acceptable range is from 0 to 600. Configuring a value of 0 disables duplicate
address detection processing on the specified interface; a value of 1 configures a single transmission without follow-up transmissions.
Default is one message.
|
Command Default
Duplicate address detection on unicast IPv6 addresses with the sending of one neighbor solicitation message is enabled.
Command Modes
Interface configuration
Command History
Release
|
Modification
|
12.2(4)T
|
This command was introduced.
|
12.0(21)ST
|
This command was integrated into Cisco IOS Release 12.0(21)ST.
|
12.0(22)S
|
This command was integrated into Cisco IOS Release 12.0(22)S.
|
12.2(14)S
|
This command was integrated into Cisco IOS Release 12.2(14)S.
|
12.2(28)SB
|
This command was integrated into Cisco IOS Release 12.2(28)SB.
|
12.2(33)SRA
|
This command was integrated into Cisco IOS Release 12.2(33)SRA.
|
12.2(33)SXH
|
This command was integrated into Cisco IOS Release 12.2(33)SXH.
|
15.2(2)SNG
|
Th is command was implemented on the Cisco ASR 901 Series Aggregation Services devices.
|
15.2(2)SA2
|
This command was implemented on the Cisco ME 2600X Series Ethernet Access Switches.
|
Usage Guidelines
Duplicate address detection verifies the uniqueness of new unicast IPv6 addresses before the addresses are assigned to interfaces
(the new addresses 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 2462, 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 2461, Neighbor Discovery
for IP Version 6 [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."
Note
|
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 message similar to the following is issued:
%IPV6-4-DUPLICATE: Duplicate address FE80::1 on Ethernet0
If the duplicate address is a global address of the interface, the address is not used and an error message similar to the
following is issued:
%IPV6-4-DUPLICATE: Duplicate address 3000::4 on Ethernet0
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).
Duplicate address detection is performed on all multicast-enabled IPv6 interfaces, including the following interface types:
-
ATM permanent virtual circuit (PVC)
-
Cisco High-Level Data Link Control (HDLC)
-
Ethernet, Fast Ethernet, and Gigabit Ethernet
-
FDDI
-
Frame Relay PVC
-
Point-to-point links
-
PPP
Examples
The following example configures five consecutive neighbor solicitation messages to be sent on Ethernet interface 0 while
duplicate address detection is being performed on the tentative unicast IPv6 address of the interface. The example also disables
duplicate address detection processing on Ethernet interface 1.
Device(config)# interface ethernet 0
Device(config-if)# ipv6 nd dad attempts 5
Device(config)# interface ethernet 1
Device(config-if)# ipv6 nd dad attempts 0
Note
|
Configuring a value of 0 with the
ipv6
nd
dad
attempts command disables duplicate address detection processing on the specified interface; a value of 1 configures a single transmission
without follow-up transmissions. The default is one message.
|
To display the state (OK, TENTATIVE, or DUPLICATE) of the unicast IPv6 address configured for an interface, to verify whether
duplicate address detection is enabled on the interface, and to verify the number of consecutive duplicate address detection,
neighbor solicitation messages that are being sent on the interface, enter the
show
ipv6
interface command:
Device# show ipv6 interface
Ethernet0 is up, line protocol is up
IPv6 is stalled, link-local address is FE80::1 [TENTATIVE]
Global unicast address(es):
2000::1, subnet is 2000::/64 [TENTATIVE]
3000::1, subnet is 3000::/64 [TENTATIVE]
Joined group address(es):
FF02::1
FF02::2
FF02::1:FF00:1
MTU is 1500 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ND DAD is enabled, number of DAD attempts: 1
ND reachable time is 30000 milliseconds
ND advertised reachable time is 0 milliseconds
ND advertised retransmit interval is 0 milliseconds
ND router advertisements are sent every 200 seconds
ND router advertisements live for 1800 seconds
Hosts use stateless autoconfig for addresses.
Ethernet1 is up, line protocol is up
IPv6 is stalled, link-local address is FE80::2
Global unicast address(es):
2000::2, subnet is 2000::/64
3000::3, subnet is 3000::/64
Joined group address(es):
FF02::1
FF02::2
FF02::1:FF00:1
MTU is 1500 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ND DAD is disabled, number of DAD attempts: 0
ND reachable time is 30000 milliseconds
ND advertised reachable time is 0 milliseconds
ND advertised retransmit interval is 0 milliseconds
ND router advertisements are sent every 200 seconds
ND router advertisements live for 1800 seconds
Hosts use stateless autoconfig for addresses.