Nodes - hosts and routers – have IP addresses and additionally MAC addresses
that identify each adapter. Each transmitted IP datagram, including source
and destination IP addresses, is encapsulated in MAC frame with the appropriate
source and destination MAC addresses.
Let us now examine the following example where the station A wants to send
a packet to the station B. As the packet travels along the path from the
station A to station B, the IP and MAC addresses in the packet should be
dragged in the correct fields. Please note, that the IP addresses are used
for end-to-end transmission at the network layer while the MAC addresses
are link-layer addresses and therefore used only in a subnet.
If you have filled in the correct addresses, the packet will move forward
to the next link!