#Cisco mac address lookup how to

In this example, the receiver is not on the same subnet. This is accomplished by checking the destination IP address against the local subnet. The sender performs a simple check to verify if the receiving device is on the same subnet. Before the sender has the ability to encapsulate any data, it must first understand where the destination is located. Figure 2-2 illustrates the first step in this process. To better explain what happens to a packet traversing the network, we will walk you through the Layer 2 and Layer 3 transmission process. From a Layer 2 perspective, this is only part of the story. In that chapter, you learned the uniqueness of IP multicast packets compared to unicast and broadcast packets. The diagrams in Chapter 1 show much of this processing in action.

#Cisco mac address lookup how to

A data transmission at Layer 4 is called a segment, a packet at Layer 3, and a frame at Layer 2.Īt each step through a network, routers and switches use these encapsulation headers and footers to make decisions about how to treat data transmissions. This allows data to be passed physically to the appropriate machine or the next hop in a network. Finally, Layer 2 adds hardware forwarding information (source and destination MAC addresses). Layer 3 adds logical forwarding details (source and destination IP addresses) so that networking devices can determine the best path toward a destination.

This allows an operating system to forward data to an appropriate application or subroutine. For example, TCP port 80 is typically web traffic. This information is encapsulated in TCP and/or UDP with specific port numbers. Take a look at Figure 2-1 to understand how this works.įigure 2-1 OSI Model and Data Encapsulationĭata from the application, presentation, and session layers (Layers 1, 2, and 3) is encapsulated at Layer 4 with transport protocol information. At each layer of the OSI reference model, the data is processed, encapsulated, and sent to the next layer. This information is added in the form of headers and footers. Think of it like an onion, with many layers. Encapsulation is the method by which information is added at each layer of the OSI reference model, used for processing and forwarding purposes. Encapsulation is an important component of the OSI model for data communication and is absolutely essential in IP networks. Layered Encapsulationīefore reviewing multicast in Layer 2, we must discuss fundamental packet-forwarding concepts to establish a baseline of the process. This chapter covers the basic elements of multicast functionality in Layer 2 domains as well as design considerations for multicast deployments. This chapter takes an in-depth look at IP multicast messages at Layer 2 and how they are transported in a Layer 2 domain. Destination Address Address Type VLAN Destination PortĠ 1, “Introduction to IP Multicast,” examined the differences between unicast, broadcast, and multicast messages. If you were looking for a device you could ping it, look at the arp table to get the mac then use the mac command to find the port.

It is used to record a stations mac address and it’s corresponding switch port location.'Įxample: Port 17 has a device plugged in with this mac address. Here is a quote from 'The CAM table, or content addressable memory table, is present in all Cisco Catalysts for layer 2 switching. I know you don't want to know about the ARP command but this command and the ARP command together you can find devices on your switches. I'm not sure why it's labeled Destination Address. The MAC table or CAM table only records source addresses. It identifies the mac address that is on that port. The column title in the command is a destination address. It will show multiple MAC addresses on the uplink port that connects to other switches. That's why I showed it two different ways. Some switches/ios versions have a slight variation of the command.

Show mac-address table or show mac-address-table will give you the interface (the given name, not the name you assign it) and MAC Addresses.