Packet Tracer file (PT Version 7.1): https://bit.ly/2vFzGUU Get the Packet Tracer course for only $10 by clicking here: https://goo.gl/vikgKN Get my ICND1 and ICND2 courses for $10 here: https://goo.gl/XR1xm9 (you will get ICND2 as a free bonus when you buy the ICND1 course). For lots more content, visit http://www.davidbombal.com - learn about GNS3, CCNA, Packet Tracer, Python, Ansible and much, much more. #CCNA #PacketTracer #CCENT The MAC address table contains address information that the switch uses to forward traffic between ports. All MAC addresses in the address table are associated with one or more ports. The address table includes these types of addresses: •Dynamic address: a source MAC address that the switch learns and then ages when it is not in use. •Static address: a manually entered unicast address that does not age and that is not lost when the switch resets. The address table lists the destination MAC address, the associated VLAN ID, and port number associated with the address and the type (static or dynamic). By default, MAC address learning is enabled on all interfaces and VLANs on the router. You can control MAC address learning on an interface or VLAN to manage the available MAC address table space by controlling which interfaces or VLANs can learn MAC addresses. Before you disable MAC address learning, be sure that you are familiar with the network topology and the router system configuration. Disabling MAC address learning on an interface or VLAN could cause flooding in the network. Transcription: So again, when a switch boots up, it doesn’t know where devices are in the topology. It has to learn where they are or you’ve got to configure the switch statically with MAC addresses. Switch has booted up doesn’t know where anyone is in the topology. At the moment on PC 1, it’s configured with this IP address but notice the ARP cache is empty. It doesn’t know the MAC address of PC 2. So if I send a ping to PC 2 now using simulation mode, what you’ll notice is the PC sends an ARP message into the network so that it can learn where PC 2 is. Again, at this point of the switch only knows where PC 1 is. When PC 2 replies, the packet is forwarded to PC 1 only because the switch knows where PC 1 is, but also now knows where PC 2 is, so all subsequent packets are sent only between PC 1 & PC 2. If I clear the MAC address table, that process will happen again. So show mac address-table If for example, PC 3 pings PC 4, it has to send an ARP message into the network to learn where PC 4 is. So it’s sending a broadcast from itself looking for the MAC address of PC 4. So the same process will apply here. Packet is flooded but the ARP packet is dropped up by PC 1 & PC 2, only PC 4 will reply to the ARP packe ... https://www.youtube.com/watch?v=GmwqU2k-YuY