Oh heck yeah now this is what I'm talking about! Data link layer shenanigans!!
For that of you who have no idea what the Address Resolution Protocol (ARP) is, to a first approximation it is the missing link between your MAC address (what Ethernet runs on) and your IP address (what Internet runs on). After your IP routing table, which you can see with `route`, decides what immediate next IP address to forward a packet to, then your ARP cache, which you can see with `arp`, will decide which MAC address that IP correspond to (usually your router's local IP address).
Knowing that ARP even exists is considered mild esoterica today, to say nothing of its IPv6 sibling the Network Discovery Protocol. But even though you don't use it much in modern cloud-based deployments, knowing it exists makes your bird's eye view of how the whole network stack works that much more holistic.
For that of you who have no idea what the Address Resolution Protocol (ARP) is, to a first approximation it is the missing link between your MAC address (what Ethernet runs on) and your IP address (what Internet runs on). After your IP routing table, which you can see with `route`, decides what immediate next IP address to forward a packet to, then your ARP cache, which you can see with `arp`, will decide which MAC address that IP correspond to (usually your router's local IP address).
Knowing that ARP even exists is considered mild esoterica today, to say nothing of its IPv6 sibling the Network Discovery Protocol. But even though you don't use it much in modern cloud-based deployments, knowing it exists makes your bird's eye view of how the whole network stack works that much more holistic.