With the purpose of registering many users on a big network (~600 users), each user's IP and MAC are needed. Currently, I am using arp command to retrieve the MAC, but for some users, I recieve an "incomplete" response. An example output:
LucasKobo.rede ether 3c:77:e6:d2:31:eb C eth0 android-b83812fa0aa8e77 (incomplete) eth0
Why is the arp response incomplete? And is there a fail proof way of getting each users MAC and IP on the application layer?