- 01Getting Started
- 02Understanding the Operating Modes of Network Devices
- 03Entering Privileged EXEC Mode with enable
- 04Entering Configuration Mode with configure terminal
- 05Renaming the Switch with hostname
- 06Moving Between Modes with exit and end
- 07Entering Port Configuration with interface
- 08Enabling a Port with no shutdown
- 09Assigning an IP Address with ip address
- 10Labeling a Port with description
- 11Viewing the Configuration with show running-config
- 12Listing Interfaces with show ip interface brief
- 13What Is a VLAN? Splitting a Network Logically
- 14Creating a VLAN with vlan
- 15Naming a VLAN with name
- 16Setting the Port Type with switchport mode
- 17Assigning a Port to a VLAN with switchport access vlan
- 18Listing VLANs with show vlan brief
- 19Adding a Static Route with ip route
- 20Viewing the Routing Table with show ip route
- 21Testing Reachability with ping
- 22Tracing the Path with traceroute
- 23Checking OS Information with show version
- 24Checking the Time with show clock
- 25Saving the Configuration with copy running-config startup-config
- 26Saving with write memory (the Short Form)
- 27Setting a Login Message with banner motd
- 28Configuring the Console Line with line console 0
- 29Setting a Password with password
- 30Requiring the Password at Login with login
- 31Configuring Remote Access with line vty 0 4
- 32Creating an Access List with access-list
- 33Checking Access Lists with show access-lists
- 34Viewing the MAC Address Table with show mac address-table
- 35Discovering Neighbors with show cdp neighbors
- 36Viewing the ARP Table with show arp
- 37Understanding Loop Prevention with spanning-tree mode
- 38Rebooting the Device with reload
- 39Hands-On: Configure a Small Office Network
Viewing the ARP Table with show arp
When you want to know which MAC address actually answers for an IP address, use show arp. It displays the ARP table — the recorded mapping between IP addresses and MAC addresses.
The syntax is show arp, in privileged EXEC mode.
Running show arp lists, for every device this one has communicated with on the local network, its IP address, MAC address, and how long ago the entry was learned.
A common stumble is assuming a device missing from the ARP table is unreachable. A device that simply hasn't communicated yet won't appear — that's all it means.
In real work, it is a staple of investigations into duplicate IP addresses and of confirming whether a given host really exists on the local network.
🧑💻 You can type this command into the Networking pseudo terminal to try it yourself (this page itself has no interactive terminal).