arp: packet with invalid ethernet address length 0 received on em0

[drwoodcomb]

Everyday I get an email with security output. In that email I get a message

Code:

arp: packet with invalid ethernet address length 0 received on em0

Can someone please explain to me what this is and if I need to be worried about it? I tried googling it but did not find any information

 

[dlavigne]

Is that system exposed to the Internet (not protected by a firewall)?

 

[drwoodcomb]

Is that system exposed to the Internet (not protected by a firewall)?

Im no networking expert, far from it infact, but as far as I know its not exposed.

The freenas box has a Supermicro C9SCM-IIF motherboard with two connections in use, one for ethernet and the other for IPMI. Both are connected to my router (Netgear 7000) through a switch (TP-LINK TL-SG108PE).

One ethernet cable is connected to em0 which is how the box is connected to my home network.

The other ethernet cable goes to IPMI

I dont have any port forwarding rules for the freenas box since I dont need to connect to it from outside my home network.

Do you have any recommendations on how I could check to see if the freenas box is exposed?

Thanks for your feedback

 

[dlavigne]

Were you able to resolve this?

 

[drwoodcomb]

Were you able to resolve this?

Thanks for checking back, but unfortunately I'm completely stumped.

I checked my router to make sure I didnt have port forwarding to the ip address of my freenas box, which I didnt, but aside from that I dont know what else to do.

Here is this mornings security report which is consistenly shows that error.


freenas.local kernel log messages:
arp: packet with invalid ethernet address length 0 received on em0
mlx4_en: mlxen0: Link Up
mlxen0: link state changed to UP
mlx4_en: mlxen0: Link Down
mlxen0: link state changed to DOWN
arp: packet with invalid ethernet address length 0 received on em0
mlx4_en: mlxen0: Link Up
mlxen0: link state changed to UP
mlx4_en: mlxen0: Link Down
mlxen0: link state changed to DOWN
arp: packet with invalid ethernet address length 0 received on em0


mlx4_en is an SFP+ 10gigabit connection that is dirrectly connected to my desktop computer so the link goes UP and Down everytime I turn my desktop on and off so that security message is expected but I still have no idea whats causing this other security message.

 

[dlavigne]

If you're only getting single arp messages around the time of the link up/down, I think you can safely ignore it. If you were getting constantly spammed by hundreds of those errors, that would be an issue to look into.