If the MAC address is found in the table, the switch will forward the packet out only on the interface associated with that MAC address in its table.
Check its MAC address table for the MAC address of the destination.So when a switch receives a (unicast) packet, it will go through the following steps: To do this, a switch keeps a MAC address table that matches MAC addresses to the ports on which those addresses appear. On the other hand, a switch is an intelligent device that is able to forward packets only to the port on which the destination device belongs. If I ping from PC1 to PC2 while capturing on the link between the hub and PC3, I will see those ping packets also being sent out to PC3 (even though that device will ignore them as they are not addressed to it): We can easily see this by looking at a simple lab in GNS3: Relevant to our discussion is the fact that when a hub receives a packet, it forwards that packet to all ports on that hub (except the port on which the packet was received), whether that packet is destined to the devices connected to those ports or not.įor example, if PC1 wants to send a packet to PC2, the hub will forward that packet out both ports 2 and 3, even though PC3 has no business with that packet. If you have been in the networking industry even for a bit, then you have probably heard of the difference(s) between a hub and a switch. We will then consider a way to make packets meant for one segment of a network to “appear” on another part of the network, aiding in effective capturing of packets. However, Packet Capturing can be challenging on a switched network and we will discuss why in this article. One of the most useful techniques available to network engineers is Packet Capturing, but in order to do this, We'll need to dig into How to do it using a popular Technique called Port Mirroring.īy looking into the packets as they are sent across a network, a couple of interesting things become possible including deep troubleshooting of network issues, security monitoring and investigation, and also the ability to learn about various technologies.
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