ARP request

ARP requests are never forwarded to reach the end host in IP-routed networks. [original post]

“There will never be an ARP request from “the internet” asking about the address for one of your hosts. IP addresses are used for end-to-end routing. Hardware addresses are used only for single hops. So if some host on the internet sends a ping, every router along the way will look at the destination IP address, consult its routing table for the next hop (IP address) in the right direction, and send the packet to the next hop host or router. To do that very last step (forward the packet to the next hop), the router needs to know the hardware address of the next hop. But it does not need to know the hardware address of the destination host. This means that arp requests are never forwarded. They are only generated for IP addresses that are directly attached to the router that is sending the request. So no router except yours will ever send an arp request for the hosts that are serviced by your router.”

ARP request for address 0.0.0.0 means that each host which receives the request must reply. [original post]

“The address ‘0.0.0.0’ is the ‘any’ address. That means, ‘any’ host should answer that request.”