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
no 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 6.0
|
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
.
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 &HundredGigE;
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/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# interface HundredGigE0/2/0/1
RP/0/RP0/CPU0:router(config-if)# ipv6 nd dad attempts 1
RP/0/RP0/CPU0:router(config-if)# Uncommitted changes found, commit them before exiting(yes/no/cancel)? [cancel]:y
RP/0/RP0/CPU0:router# show ipv6 interface
HundredGigE/2/0/0 is Up, line protocol is Up
IPv6 is disabled, link-local address unassigned
No global unicast address is configured
HundredGigE/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.
HundredGigE/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/RP0/CPU0:router(config)# dynamic-template type ppp p1
RP/0/RP0/CPU0:router(config-dynamic-template-type)# ipv6 nd dad attempts 1