Deliver frames on a local network
Distinguish link-layer addresses from network addresses.
- Describe how a switch uses MAC addresses to forward local frames.
On a typical Ethernet LAN, a frame carries source and destination MAC addresses. A switch learns which source MAC addresses arrive on each port and uses that table to forward later frames. MAC delivery is local to a link; IP addresses identify endpoints across networks. Address resolution connects the two on an IPv4 LAN.
switch_table = {"aa:10": "port 1", "bb:20": "port 2"}
destination = "bb:20"
print(switch_table.get(destination, "flood local ports"))port 2
If a switch does not know a destination MAC, it usually floods the frame to the other ports in that VLAN, then learns from the reply. ARP is one IPv4 mechanism used to discover a local MAC address for a next-hop IP address.
Key takeaways
Describe how a switch uses MAC addresses to forward local frames.
The code examples simulate protocol behavior; they do not send network traffic.
Use the layer model to locate where an address, port, or message belongs.
Lesson quiz
4 questions · pass with 3 correct · up to 50 XP
Passing this quiz completes the lesson and keeps your streak going. Questions you miss come back in review sessions later.
Practice: model networking concepts
Use small Python programs to model packet, address, and protocol behavior. These exercises run locally in your browser and do not send network traffic.
Look up a switch port
Use the learned MAC table to print the destination port, or flood local ports when the address is unknown.
- Known destination
- Unknown destination
Python runs in a sandboxed browser worker with a 60 second time limit. Its runtime loads from the Pyodide CDN; your code stays in this browser.
Questions about this lesson
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