Question about ARP as presence detection

[DAVIZINHO]

Hello,
I use a script to know if my devices are connected at my network.
Now I use this command:
arp -i br0 -na | awk '{print $4}'

This give to me a list of macs that connect to my network.

The problem is that i have one device connected that i can see in asus web interface but not apears in this arp list

this is normal? any solution? other command that works for my idea?

thanks

 

[ColinTaylor]

What is the device? Is it asleep?

Entries in the ARP table will expire after a while, that's normal. So unless there is traffic going to or from the device in question it's quite possible its ARP entry has been removed.

 

[DAVIZINHO]

The devices is a AVR amplifier (harman/kardon). Not have a lot of trafic in the network interface, but while i launch de arp command, i make ping -t and reply all the pings
i dont understand :-(

 

[ColinTaylor]

How is it connected, wired or wireless?

 

[RMerlin]

Check the raw content of the arp cache:

cat /proc/net/arp

 

[DAVIZINHO]

How is it connected, wired or wireless?

wired

Check the raw content of the arp cache:

cat /proc/net/arp

Not apears the device, but i can see it in when i press "view list" in network map in web interface
Is extrange! :-

 

[ColinTaylor]

wired

If it's in ports 5-8 try moving it to ports 1-4.

 

[DAVIZINHO]

If it's in ports 5-8 try moving it to ports 1-4.

I will check in wich port is connected but i think this is not the problem
The "ghost device" is connected in a aditional switch, and in this switch are connected 2 devices more (a tv and a sat receiver) that apears perfectly in the arp