ipv6 nd dad attempts (BNG)
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 an appropriate configuration mode. To return the number of messages to the default value, use the no form of this command.
ipv6 nd dad attempts value
Syntax Description
value |
Number of neighbor solicitation messages. Range is 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. |
Command Default
Duplicate address detection on unicast IPv6 addresses with the sending of one neighbor solicitation message is enabled. The default is one message.
Command Modes
Interface configuration (not applicable for BNG)
Dynamic template configuration (for BNG)
Command History
Release |
Modification |
---|---|
Release 4.3.0 |
This command was supported in the dynamic template configuration mode for BNG. |
Release 3.7.2 |
This command was introduced. |
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 the sending of 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 the address is being resolved or when the reachability of a neighbor is being probed. 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.
For BNG, ensure you run this command in the dynamic template configuration mode. To enter the dynamic template configuration mode, run dynamic-template command in the Global Configuration mode.
![]() 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_nd[145]: %IPV6_ND-3-ADDRESS_DUPLICATE : Duplicate address 111::1 has been detected
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 GigabitEthernet
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).
Task ID
Task ID |
Operations |
---|---|
ipv6 |
read, write |
config-services |
read, write |
Examples
This example (not applicable for BNG) shows how to set the number of consecutive neighbor solicitation messages for interface 0/2/0/1 to 1 and then display the state (tentative or duplicate) of the unicast IPv6 address configured for an interface:
RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router(config)# interface gigabitethernet 0/2/0/1
RP/0/RSP0/CPU0:router(config-if)# ipv6 nd dad attempts 1
RP/0/RSP0/CPU0:router(config-if)# Uncommitted changes found, commit them before exiting(yes/no/cancel)? [cancel]:y
RP/0/RSP0/CPU0:router# show ipv6 interface
gigabitethernet2/2/0/0 is Up, line protocol is Up
IPv6 is disabled, link-local address unassigned
No global unicast address is configured
gigabitethernet2/2/0/1 is Up, line protocol is Up
IPv6 is enabled, link-local address is fe80::203:fdff:fe1b:4501
Global unicast address(es):
1:4::1, subnet is 1:4::/64 [DUPLICATE]
MTU is 1514 (1500 is available to IPv6)
ICMP redirects are disabled
ND DAD is enabled, number of DAD attempts 1
ND 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.
gigabitethernet2/2/0/2 is Shutdown, line protocol is Down
IPv6 is enabled, link-local address is fe80::200:11ff:fe11:1111 [TENTATIVE]
Global unicast address(es):
111::2, subnet is 111::/64 [TENTATIVE]
MTU is 1514 (1500 is available to IPv6)
ICMP redirects are enabled
ND DAD is enabled, number of DAD attempts 1
ND 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.
For BNG, this example shows how to display the state (tentative or duplicate) of the unicast IPv6 address on the dynamic template configuration mode:
RP/0/RSP0/CPU0:router(config)# dynamic-template type ppp p1
RP/0/RSP0/CPU0:router(config-dynamic-template-type)# ipv6 nd dad attempts 1