Re: ARP Address Conflict Detection and dhcpcd arping

[Andy Ruhl <acruhl%gmail.com@localhost>]

On Fri, Oct 11, 2019 at 4:41 AM rudolf <netbsd%eq.cz@localhost> wrote:
>
> Hi,
>
> I have a NetBSD 8.1_STABLE (july 2019) host with a static IP address and
> another machine (Linux) with dhcpcd "arping" configuration for this IP
> address. With the default value of sysctl net.inet.ip.dad_count (=3), I
> see no ARP reply ("ARP, Reply <IP addr> is-at <MAC>") messages from the
> NetBSD host on the arping queries ("ARP, Request who-has <IP addr> tell
> 0.0.0.0") and eventually the NetBSD host marks its IP address as
> duplicated (and the "arping" dhcpcd configuration of the second host fails).
>
> This seems contradictory to what I read in "man 4 arp":
> ``ARP will defend the host's active address when a conflicting message
> is received.''
>
> With "sysctl -w net.inet.ip.dad_count=0", the NetBSD host sends the ARP
> reply and the "arping" configuration of the second host works.
>
> Is this expected behavior?

I did a manual arping -D <ip> from an already configured Linux machine
to my 8.0 NetBSD machine and the arp was replied to right away. Can
you try the same thing? It did say reply 0.0.0.0 so it should be
pretty similar to what you're doing.

Andy