Chapter 27
| IP Interface Commands
IPv6 Interface
– 774 –
◆ Duplicate address detection determines if a new unicast IPv6 address already
exists on the network before it is assigned to an interface.
◆ Duplicate address detection is stopped on any interface that has been
suspended (see the vlan command). While an interface is suspended, all unicast
IPv6 addresses assigned to that interface are placed in a “pending” state.
Duplicate address detection is automatically restarted when the interface is
administratively re-activated.
◆ An interface that is re-activated restarts duplicate address detection for all
unicast IPv6 addresses on the interface. While duplicate address detection is
performed on the interface’s link-local address, the other IPv6 addresses remain
in a “tentative” state. If no duplicate link-local address is found, duplicate
address detection is started for the remaining IPv6 addresses.
◆ If a duplicate address is detected, it is set to “duplicate” state, and a warning
message is sent to the console. If a duplicate link-local address is detected, IPv6
processes are disabled on the interface. If a duplicate global unicast address is
detected, it is not used. All configuration commands associated with a
duplicate address remain configured while the address is in “duplicate” state.
◆ If the link-local address for an interface is changed, duplicate address detection
is performed on the new link-local address, but not for any of the IPv6 global
unicast addresses already associated with the interface.
Example
The following configures five neighbor solicitation attempts for addresses
configured on VLAN 1. The show ipv6 interface command indicates that the
duplicate address detection process is still on-going.
Console(config)#interface vlan 1
Console(config-if)#ipv6 nd dad attempts 5
Console(config-if)#end
Console#show ipv6 interface
VLAN 1 is up
IPv6 is enabled.
Link-local address:
fe80::269:3ef9:fe19:6779%1/64
Global unicast address(es):
2001:db8:0:1:2e0:cff:fe02:fd/64, subnet is 2001:db8:0:1::/64[EUI]
2001:db8:2222:7272::72/96, subnet is 2001:db8:2222:7272::/96
Joined group address(es):
ff02::2
ff02::1:ff19:6779
ff02::1:ff00:0
ff02::1:ff00:72
ff02::1:ff02:fd
ff02::1:2
ff02::1
IPv6 link MTU is 1500 bytes
ND DAD is enabled, number of DAD attempts: 5.
ND retransmit interval is 1000 milliseconds
ND advertised retransmit interval is 0 milliseconds
ND reachable time is 30000 milliseconds
ND advertised reachable time is 0 milliseconds
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