AddressResolution Protocol from CMD prompt..: A question.

Just found out about the 'ARP -a' command available in CMD Prompt.

Was wondering why there is more than one MAC Address listed?

I recognise my router as one of the MAC addresses (the only 'dynamic' address listed). However there are 4 'static' MAC addresses listed there as well. I don't recognise these IP addresses or MAC addresses.

Could anyone explain as to how to trace the source of these addresses? When I delete them they reappear on the next system boot and one of them, in particular, does not disappear from the list when I execute the delete command.

Maybe there's a system file (DLL file or similar) that is responsible for saving the list of addresses? Perhaps a different way to explain these anomalous addresses?

Appreciate your assistance.

Bree said:

There is. They are Multicast addresses and, like the 192.168.***.*** range of IP addresses, are Private address ranges. These are reserve for internal use on your own network only.

Multicast address - Wikipedia

So they essentially broadcast packets to all connected devices within the local network only and don't, for example, broadcast packets across the router, onto the wider internet? Multicast can be notoriously public for anyone who cares to listen for it, so I'm concerned that they stay within the confines of the network.

How can I delete these multicast addresses since I'm not using them?

Why are the MAC Addresses associated with these multicast addresses not recognizable? What devices do they refer to?

Bree said:

I don't think you can (or should) delete them. From that Wikipedia article's table of Notable Addresses...

IP multicast address	Description	Routable
224.0.0.22	Internet Group Management Protocol (IGMP) version 3	No
224.0.0.251	Multicast DNS (mDNS) address	No
224.0.0.252	Link-local Multicast Name Resolution (LLMNR) address	No
239.255.255.250	Simple Service Discovery Protocol address	Yes

Their associated MAC addresses are group addresses, rather than the individual address of an NIC.

MAC address - Wikipedia

Alright, I'll continue to research why they're there by default.

Anyone else who can further clarify would be appreciated.

I deleted 2 of the 3 successfully. One won't delete at all (despite the '-d' command claiming successful execution). What file contains the data for this list of MAC-to-IP results?. They reappear on subsequent system reboots.