Ip – Does every host on the LAN share the same ARP table, or do hosts keep them individually

arpipip addressipv4mac address

I'm just learning about ARP. I'm a little bit confused. My confusion is better explained in a scenario.

Host A is communicating with Host B. Host A knows Host B's IP address, but not it's MAC address. Therefore, it send an ARP request to the LAN and Host B replies with its Mac address. So now Host A is aware of Host B's Mac address, and can make an entry with Host B's Mac address into an ARP table.

My questions regarding the ARP table

  1. Is Host A updating its own ARP table, or a shared ARP table amongst the entire LAN?

** Question 2 is only applicable if the answer to question 1 is "each host keeps their own ARP table"

  1. If the ARP able is not shared amongst all the LAN, would other hosts on the same LAN be made aware of this new information that Host A just received, if those other hosts did not have it already?
    • Let me expand on this: Let's assume a Host C and Host D. Now that Host A has entered Host B's MAC into its ARP table, would Host C and Host D be made aware of Host B's MAC address in their respective ARP tables?

Best Answer

Actually, every interface in a device has its own ARP table. A host could have several ARP tables (one for each interface it has). ARP tables are not shared between hosts, or even among interfaces in the same host, but a host may hear ARP traffic on the network and update the ARP table of the interface where the ARP traffic is heard.

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