Query on ARP broadcast mac-address?

[mtsb]

Hi all,

I have a basic doubt in ARP packet being sent from a router. In the ethernet frame of the ARP packet I see the Destination MAC address as FF:FF:FF:FF:FF:FF. But in the actual ARP header I see the Target MAC address as 00:00:00:00:00:00. Does both all FFs and all 0s signify broadcast mac-address?

Thanks,

Madhu

[Peter Paluch · Accepted solution]

Madhu,

The Target MAC address inside the ARP message body is a compulsory field so it cannot be omitted. However, when you are resolving the target's MAC addres then obviously you do not know it, and that is the reason that the Target MAC field in the ARP message is present but zeroed (i.e. unspecified).

Best regards,

Peter

[mtsb]

Hi Peter,

Ok cool. So I have to assume that all 0s is just there to fill in that particualtar target mac-address field and it does  not represent a broadcast mac-address.

Thanks Peter for clarification and I will consider this question answered.

Thanks again,

Madhu