3 x NA from host sent immediately after getting an RA ?

vom513 vom513 at gmail.com
Tue Aug 20 00:22:55 CEST 2024


Hello all,

I am playing with some ancient things - and one of them is a NetBSD/sparc 10.0 machine dialing up with analog modem into an (also ancient) Cisco router.  This is all a small self contained lab I have here using a line sim.

In any case, I not only managed to get this working - I got IPv6 working.

Something that struck me as curious (could just be ignorance) - is that right after getting an RA on the ppp link, my host sends 3 NA’s.  These have override set (so is this roughly the equivalent of an IPv4 gratuitous ARP ?).

Here is the pcap if anyone wants to see: https://burn.net/dad.pcap

Furthermore, the host then complains about a duplicate address on the link. (it’s own).

So my first question is - is this behavior documented in an RFC anywhere ?

And the second question is likely NetBSD specific - it seems like somehow these packets are “reflected” back to me on the PPP link ?  I don’t see them come back in a capture running but that doesn’t mean they don’t come in.  The machine has no issues of the sort using ethernet for IPv6.

Also FYI - in NetBSD 10, dhcpcd is used to solicit SLAAC/DHCPv6/RAs etc.  I am doing SLAAC on the ppp link.  So LL from IPv6CP and then dhcpcd sends an RS.  There still is some kernel responsibility, but most of the these mechanics are now handled by the dhcpcd client.

Thanks for any info.


More information about the ipv6-ops mailing list