KB.15.15

performed while DAD is disabled, the duplicate address check is not performed

on any IPv6 addresses configured on the switch.

Default: 3 (enabled); 0 (disabled); Range: 0 - 255 (0 = disabled)

The no form of the command restores the default setting (3).

NOTE: Software version K.14.xx supports a dad-attempts range of 0 to 600.

However, software version K.15.xx or greater supports a range of 0 to 255. If

dad-attempts is set higher than 255, updating from K.14.xx to K.15.xx or

greater and rebooting truncates this value to 255. Similarly, if the switch is running

version K.15.xx or greater: (1) downloading a configuration file created using

version K.14.xx with dad-attempts set higher than 255 and then (2) rebooting

the switch using this configuration file truncates the setting to 255.

Syntax:

ipv6 nd ns-interval milliseconds

Used on VLAN interfaces to reconfigure the ND time in milliseconds between DAD

neighbor solicitations sent for an unresolved destination, or between duplicate

address detection neighbor solicitation requests. Increasing this setting is indicated

where neighbor solicitation retries or failures are occurring, or in a "slow" (WAN)

network.

This value can be configured in a router advertisement to help ensure that all hosts

on a VLAN are using the same retransmit interval for ND. See “Setting or changing

the Neighbor Discovery retransmit timer” (page 189).

To view the current setting, use show ipv6 nd.

Default: 1000 ms; Range: 1000 to 3600000 ms

Syntax:

ipv6 nd reachable-time milliseconds

Used on VLAN interfaces to configure the length of time in milliseconds a neighbor

is considered reachable after the Neighbor Unreachability Detection algorithm has

confirmed it to be reachable. When the switch operates in host mode, this setting

can be overridden by a reachable time received in a router advertisement.

This value can be configured in an RA a router advertisement to help ensure that

all hosts on a VLAN are using the same reachable time in their neighbor cache.

To view the current setting, use show ipv6 nd.

Default: 30000 ms; Range: 1000 to 2147483647 ms

Operating notes for ND

• A verified link-local unicast address must exist on a VLAN interface before the switch can run

DAD on other addresses associated with the interface.

• If a previously configured unicast address is changed, a neighbor advertisement (an all-nodes

multicast message--ff02::1) is sent to notify other devices on the VLAN and to perform DAD.

• IPv6 addresses on a VLAN interface are assigned to multicast address groups identified with

well-known prefixes.

• DAD is performed on all stateful, stateless, and statically configured unicast addresses.

• Neighbor solicitations for DAD do not cause the neighbor cache of neighboring switches to

be updated.

32 IPv6 Addressing Configuration