We can use the command: sh ip arp | i 10.10.101.12 To do this, we will need to look into the ARP table to find the MAC association.Ī. Doing this will allow us to trace the MAC-address origin within the layer 2 network. We next need to use the IP that was provided to identify the MAC address of the device. If we run the command sh ip int br | b Vlan we can locate that this is the gateway or within the subnet of the client.Ģ. Login to the core to see if the gateway is on there.Ī. Here are the steps for a basic trace to locate it.ġ. Let’s say we are looking for client 2 in the above diagram and we know that its IP address is 10.10.101.12. If you are given a MAC address and don’t know the gateway (this could happen if you are locked out of the device), then you are going to start with the device that contains the most gateways and work down from there to trace or pair the MAC address.Second, you always want to start at the gateway for the given information so if you know which device has the gateway you can start there.In most cases, you will be given an IP address and you will have to locate where it is on the network. First, we will have to start with some information, such as either the MAC address or the IP address.The goal is to trace the path to client 1 and 2 using the CAM and ARP tables. If CDP is disabled, you can use Show arp to ID the known switch IP and trace it via its MAC address using the above commands. This command is used for tracing what the switch IP address of the next hop to the destination IP is. Show cdp neighbors OR Show cdp neighbors detail OR Show lldp neighbors This is most useful on a core switch or router. This is used to match up the IP address to the MAC address. This will give you the MAC and the origin port it was received on (that port is import). This command will show the internal MAC address-table of the switch or router that you are on.

To perform a trace, you will utilize the following commands: Show mac address-table OR show mac-address-table It is specifically useful when troubleshooting. This can be used whenever you are looking to verify a port for a computer or server, and it can be used to find routers, hubs, or smart switch clients. This methodology is vendor agnostic, but in this example we will be focusing on Cisco devices.

Network tracing is a basic task of using a router’s or switch’s CAM (MAC) table and ARP tables to trace the origin of an IP address or MAC address throughout a network. Network tracing can act as an extremely useful tool within any networking admin’s toolset. Back to Basics: Network Tracing Mathew Lastra | Senior Systems Architect

How to check cisco router mac address