IPv6 duplicate DAD packets from Android clients?

[Phil Mayers]

All,

Since our student body have returned, we've been seeing a trickle of:

%IPV6_ND-6-DUPLICATE_INFO: DAD attempt detected for FE80::5:73FF:FEA0:1 
on VlanNNN

...on our Cisco 6500s. The vlan points to a bunch of Cisco WLC 
controllers running 7.4 and with all the IPv6 FHS turned on.

When I capture the packets (thanks for not logging the source MAC, 
Cisco!) I see it's coming from the MAC address of a couple of Android 
devices.

Source IP is :: dest is ff02::1:ffa0:1 (obviously) and the IP is a 
HSRPv2 virtual IP on the router itself.

So, two things:

  1. Should the Cisco WLC IPv6 FHS stuff be blocking these, given the 
target IP is the HSRP VIP and is obviously not on a client? Do I need to 
be worried about them?

  2. Where are they coming from? Is the client buggy and actually 
emitting the packet, or is it relaying these somehow from another network?