Cisco CCNA Packet Tracer Ultimate labs: Spanning Tree PortFast. Answers

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PortFast causes a switch or trunk port to enter the spanning tree forwarding state immediately, bypassing the listening and learning states.

You can use PortFast on switch or trunk ports that are connected to a single workstation, switch, or server to allow those devices to connect to the network immediately, instead of waiting for the port to transition from the listening and learning states to the forwarding state.

Caution: You can use PortFast to connect a single end station or a switch port to a switch port. If you enable PortFast on a port that is connected to another Layer 2 device, such as a switch, you might create network loops

When the switch powers up, or when a device is connected to a port, the port enters the spanning tree listening state. When the Forward Delay timer expires, the port enters the learning state. When the Forward Delay timer expires a second time, the port is transitioned to the forwarding or blocking state.

When you enable PortFast on a switch or trunk port, the port is immediately transitioned to the spanning tree forwarding state.

Transcription:

Think about your PC today. How long does it take your PC to boot up?
PCs today don’t take 30 seconds to boot up. A lot of them are available within a few seconds or instantly. That’s a problem when we have technology such as Spanning Tree that take 30 seconds to converge and forward traffic on a network.

What I’m going to do is power cycle the devices and I’ll put the lab into simulation mode. Notice the switch has now booted up. Interfaces are showing orange. So what happens now is, if the PC sends a renew message, that DHCP message is going to be sent to the switch and then it’s going to drop until the ports go to green.

So once the ports go to green, the DHCP request message can be forwarded but previously, that message from PC 1 was dropped because the ports were transitioning from listening to learning to forwarding. So during that period of time, DHCP messages will be dropped by the switch.

So let’s configure Spanning Tree PortFast on the switch. On which ports do I need to configure it? I need to configure it on both the client ports and this server port. We essentially want these 3 ports in this topology to transition to the forwarding state immediately.

Okay, so here’s the switch. What I’m going ... https://www.youtube.com/watch?v=yChJzhRXo9Q