Hello Harsha
True, Gratuitous ARP is not included within the content of the lessons. It is definately a vital part of what ARP is, but it is not central to the operation of ARP. Typically, gratuitous ARP is used:
- when attempting to detect duplicate IPv4 addresses
- when updating an ARP table after an IPv4 or MAC address change
- in conjunction with FHRPs such as HSRP
You can find some information about it in a part of the following post. Note the first part of the post deals with something other than Gratuitous ARP, but the second part explains it in some detail.
If you would like to see more information or a lesson about Gratuitous ARP, feel free to submit your suggestion at the following Member Ideas link:
I hope this has been helpful!
Laz