Meaning of ff ff ff ff ff ff

none

The sending computer will of course know its source MAC address but how does it know the destination MAC address?

That’s where ARP comes into play.

Now wait a second…how does H1 know about the MAC address of H2?

We know the IP address because we typed it but there is no way for H1 to know the MAC address of H2.

There is another protocol we have that will solve this problem for us, it’s called ARP (Address Resolution Protocol).

The ARP table is empty so we have no clue what the MAC address of H2 is.

The first thing that will happen is that H1 will send an ARP Request.

This message basically says “Who has 192.168.1.2 and what is your MAC address?”

Since we don’t know the MAC address we will use the broadcast MAC address for the destination (FF:FF:FF:FF:FF:FF).

This message will reach all computers in the network.

Above you see the ARP request for H1 that is looking for the IP address of H2.

The source MAC address is the MAC address of H1, the destination MAC address is “Broadcast” so it will be flooded on the network.

Ethernet II, Src: Vmware_e7:0f:2e (00:0c:29:e7:0f:2e), Dst: Broadcast (ff:ff:ff:ff:ff:ff)