I am trying to capture some IP packets in my personal LAN with tcpdump, through the command
tcpdump -A -i eth0 'tcp and (((ip[2:2] - ((ip&0xf)<<2)) - ((tcp&0xf0)>>2)) != 0) and host 192.168.1.x'
where 192.168.1.x is the target host in the network. But it works only if the target host is my ip, that is the IP of the machine where tcpdump runs. With any other IP in the network it doesn't record anything.
I have an unmanaged switch. The simpler command
tcpdump -A 'host 192.168.1.x'
detects only some igmp packets periodically sent to a broadcasting address, 188.8.131.52, from the host 192.168.1.x.
But how could the IP capture be performed?
Thank you anyway!