Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

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The IPv6 neighbor discovery (ND) multicast suppress feature stops as many ND multicast neighbor solicit (NS) messages as possible by dropping them (and responding to solicitations on behalf of the targets) or converting them into unicast traffic. This feature runs on a layer 2 switch or a wireless controller and is used to reduce the amount of control traffic necessary for proper link operations.

When an address is inserted into the binding table, an address resolution request sent to a multicast address is intercepted, and the device either responds on behalf of the address owner or, at layer 2, converts the request into a unicast message and forwards it to its destination.

The following figure provides an overview of this feature:

The IPv6 duplicate address detection (DAD) proxy feature provides host-to-host connectivity in LANs where direct communication between hosts is not possible. For example, in a Service Provider (SP) deployment, hosts must not see each other directly on the layer 2 domain. Hosts often are added to private VLANs and then directed to the same primary VLAN to reach SP servers and devices. This process raises an issue with IPv6 DAD, especially with link-local addresses, which are auto-assigned by hosts using the IPv6 stateless address autoconfiguration ND protocol.

When a host needs to verify that its address is unique, it enables the DAD procedure. However, when the two hosts cannot communicate with each other at layer 2, this procedure cannot detect a duplicate address. If the DAD procedure cannot run, there is the slight possibility that two hosts will assign the same link-local address, which will cause both hosts to fail when they try to reach the DHCPv6 server. The IPv6 DAD proxy feature responds on behalf of the address's owner when an address is already in use.

The following figure provides an overview of the IPv6 DAD proxy feature:

1.    enable

2.    configure terminal

3.    ipv6 nd suppress policy policy-name

4.   mode dad-proxy

5.   mode full-proxy

1.    enable

2.    configure terminal

3.    interface type number

4.    ipv6 nd suppress attach-policy [policy-name [vlan {add | except | none | remove | all} vlan [vlan1, vlan2, vlan3...]]]

5.   exit

1.    enable

2.    configure terminal

3.   ipv6 nd dad-proxy