Just trying to get to grips with how arp spoofing works, and i have got a perfect setup going using ettercap to find hosts, select targets and do the arp poisoning then using wireshark to get the packets (i coudnt see the packets in ettercap graphical mode?)

But ideally i would like to use the dsniff arpspoof program to do this, but it isnt working

From a wireless linux laptop, intercepting traffic from, and traffic for that IP from the router
arpspoof -i ath0 -t
arpspoof: coudn't arp for host
Think thats correct syntax, so i need to do the above twice, tell the router that im and tell that im the router. But the commands are failing.

Both machines are on the same LAN & Subnet so i don't see why it isn't working, i can ARP spoof these IPs fine in ettercap.

Thanks for any help