Why do some links turn red when I switch from Topology to Simulation Mode?
When you switch from Topology to Simulation Mode, Packet Tracer initializes all of the devices in the network so they can function. The initialization process for hubs and repeaters is to eliminate Layer 1 loops. They remove these loops by disabling some ports in the loop. Thus some links would go down and the link lights would turn red. Switches and bridges use a similar process called the Spanning Tree Protocol (STP) to eliminate Layer 2 loops.
Related Questions
- Why is the routing table not showing up in Topology mode? Why can I configure the device in Simulation mode or Realtime mode?
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