3D Live tip: press K to freeze a ping and read the wire
A ping looks like one event. In 3D Live you can stop it on the wire and see that it isn't.
Two PCs and a router on one switch are enough, with the router's port up. Build them in the lab, press 3D Live, and go to the Send real traffic panel:
- Untick Background traffic and Control plane so your ping has the wire to itself, and let the last frames land.
- Press Flush ARP so every cache starts empty.
- Click a ping, such as PC-A → PC-C, then press K.
Everything freezes, and On the wire now lists each frame crossing a cable at that instant. Press . to step forward and , to step back, or use the Timeline's buttons. Click a row to read its addresses.
Here's what to look for:
- ARP who-has leaves PC-A, and the switch floods it toward both PC-C and the router. That's a broadcast: everyone in the VLAN hears the question.
- ARP is-at comes back from PC-C, and the switch sends it to PC-A alone. That's a unicast: the switch learned PC-A's port from the question.
- Only then does the ICMP echo request leave PC-A.
That last step is the one to notice. Your ping existed the whole time, but PC-A held it until ARP gave it a MAC address to send to.
The engine log already shows the reply while you're paused, because the simulator has finished and the animation is replaying it slowly. Press Live to return to real time.
3D Live is free on every plan and opens without an account. Start in the NetForge-AI lab, then press 3D Live.