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Subject: Re: Revisiting FreeBSD-SA-08:10.nd6 (or: avoiding IPv6 pain) 
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>However, when a packet from an "off-link" network is employed, the 
>sending node has no way of knowing where to send the packet, unless it 
>simply swaps the src and dst mac addresses, and uses the source address 
>of the packet as the destination addresses.

No, a node can just use the normal IPv6 send mechnisms to send a NA
message. If the destination is off-link then the packet gets sent to the
default router.

Then, if the default router considers the destination on-link, it will forward
the packet and send a redirect. The redirect should have a link layer address
to allow the target host to send future traffic directly.