What Is ARP?Īddress Resolution Protocol or ARP connects Internet Protocol Address (IP address) to Media Access Control address (MAC address) in a Local Area Network or LAN. This post will show you how to find all IP addresses on a network using the Mac Address. But what if you don't see the IP address of a device in a local network? Finding a Mac address is very easy if you know the IP address. In turn, the MAC is connected to FastEthernet port #40 on Switch5.Every device connected to the network including, printer, switch, router, computer, tablets, and smartphones, has an IP address and Mac address that identify it on a network. This shows the IP address 1.2.3.4 is bound to MAC address 001e.6764.7e21. Switch5>show mac address-table | include 001e.6764.7e21 Router1>show mac address-table | include 33Ĩ85 33 DYNAMIC Po5 Sample output Router1> show arp | include 1.2.3.4 Right-most entry in the table is the port in the direction of the MAC address: To do that, run: Router1> show mac address-table | include 33 You can then use the MAC address to narrow down the host by running it on the router itself and any subsequent switches in the routing table. This will tell you the MAC address of the host is 33. To find IP address 1.2.3.4, run this command on your router: Router1> show arp | include 1.2.3.4 However, in most setups, the full ARP table will only be kept on the router, so it's best to start from that. If you have a switched network and your switches are on the same VLAN as the host, you can use the switches' ARP table. If you need to track down an IP address on your network, you need to use your network devices' ARP table. This will give you a MAC address which can be used to track down the host via the MAC address table: Router1> show mac address-table | include 33 Run this command on a switch on the same VLAN or the central router: Router1> show arp | include x.x.x.x

Tracking down a specific host on your network through its IP address. Find a host through its IP address (Cisco)

Get mac address from ip