Every Ethernet interface has a 48-bit MAC address — flat, local to the link. IP lives at layer 3; to deliver frames on the same subnet hosts need to map IP→MAC. ARP (Address Resolution Protocol) broadcasts a question and caches replies in a table.

Hub vs switch vs router
DeviceBehaviorRole in switching & routing
HubRepeats electrical signal to every port — shared collision domainNo intelligence; rare today.
L2 switchBuilds a MAC→port table; floods unknown unicast and broadcast within a VLANSwitching — microsegmentation, VLANs; STP prevents bridging loops.
L3 router / L3 switchLooks at IP, decrements TTL, rewrites L2 toward next hopRouting — connects subnets; host uses gateway MAC for off-net destinations.
Full content is available with a subscription.
Get full access to all courses on the platform for one year with a single payment.
Unlike other platforms that charge per course, here you get everything for one price, and after one year of use there will be no automatic charge for the following year.