When a destination IP address is on the SAME network as the sender, whose MAC address goes in the destination MAC field?

Question

Accepted Answer

The destination MAC is the MAC address of the destination device itself — the sender resolves it directly (via ARP for IPv4 / ND for IPv6) because both hosts share the local network.
Same-network delivery rule:

Layer 2 addresses deliver frames from one NIC to another NIC on the same network.
If the destination IP is on the local network, the destination MAC = the destination device's MAC address.

How the sender knows it is local:
The sender compares the destination IP against its own IP and subnet mask. If the destination is in the same subnet, it resolves that device's MAC directly rather than the gateway's.
Why it matters: This is the contrast case to a remote destination — knowing whether the target is local or remote is what decides whose MAC address the device must resolve.
Go deeper:

Address Resolution Protocol — Wikipedia's ARP walkthrough shows a host resolving the destination's own MAC directly when both share the local network.

Traditional ARP — PracticalNetworking distinguishes the "destination" (L2 address) from the "target" (the IP being resolved) on the same segment.