Constant ARP requests

[Horizon_Brave]

Hello

I'm using a Debian distro in Windows 10, through Virtualbox. I have a NAT network, as I just need some basic functionality for now. This really isn't a problem, but more of a curiosity. I'm running a background tcpdump and I notice anytime Debian needs to make a request 'outside" (sent to 10.0.2.2 my default virtual router), I see that an ARP request for the MAC of 10.0.2.2 has to be sent. Even a ping, a traceroute, any NTP requests, etc... they all force debian to ARP out a request for the MAC. Here's a sample:

15:44:27.964752 ARP, Request who-has 10.0.2.2 tell 10.0.2.15, length 28
15:44:27.965098 ARP, Reply 10.0.2.2 is-at 52:54:00:12:35:02 (oui Unknown), length 46

This plays out each and every time Debby, needs to contact something through it's default gw. Is this expected? I checked my arp cache and it has the entry for the 10.0.2.2 gateway with it's matching MAC address.

The OUI unknown message is what's bothering me that there may be an issue with it trying to use the entry into the arp table? Any idea's?

[Valery Ushakov]

This is your guest doing normal ARP lookups, nothing VirtualBox related here.

The OUI unknown message just means that tcpdump doesn't have an entry for 52:54:00 prefix in its OUI database. It doesn't affect anything at the network level.

[Horizon_Brave]

Wait, I get that an ARP request should be sent...but why is it sent out EACH time? I have the entry in my arp cache, why does it need to resend an ARP request each time it needs to talk outside of it's network?

[Valery Ushakov]

How frequent is "each time"? It's impossible to tell anything without seeing actual packet captures. However, as I've already said, this is entirely the guest's behaviour. How the guest manages its ARP cache cannot be affected by VirtualBox.