Join Greg Sowell for an in-depth discussion in this video Arp, part of Foundations of Networking: Protocols and CLI Tools.
- [Voiceover] The ARP command is a tremendous…troubleshooting tool for ARP issues…as well as layer two troubleshooting.…ARP stands for Address Resolution Protocol…and is responsible for doing the layer three IP mapping…to layer two MAC addresses.…Whenever a computer needs to send information…to another host on a directly connected subnet,…it will first check its ARP cache.…If a mapping exists, it will send the traffic based…on this information.…If a cache is empty, it will send out an ARP request…asking for the IP's owner to send back its MAC address.…
To view the ARP cache, I issue arp -a.…If you scroll up, you can see all of the different…cached entries based on interface.…I'm gonna go ahead and clear the screen now.…Say, for example, I have a rogue DHCP server on the network.…He's handing me an IP and a default gateway.…It's a false path to the Internet.…I can do an ipconfig, space, forward slash, all,…and take note of the DHCP server that handed me the IP.…
I'll scroll up, and use my actual valid gateway…as an example.…
Protocols are the lifeblood of modern communication. By the end of this course, you'll know what you need to troubleshoot any network connection and keep the communication flowing.
Note: This course maps to domain 3 of the MTA Networking Fundamentals exam.
- The role of protocols in networking
- Port addresses
- ARP and InARP
- DNS and NetBIOS
- HTTP and HTTPS
- Mail protocols
- Using command-line tools to troubleshoot protocols and routing