AddressResolution Protocol from CMD prompt..: A question.

  1. Thelps's Avatar
    Posts : 106
    Windows
       #1

    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.
      My Computer


  2. Posts : 264
    Windows 10
       #2

    MAC addresses are not dynamic. You will get one for each network adapter in your computer, included virtual ones, from Microsoft and other vendors.
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  3. Bree's Avatar
    Posts : 18,600
    10 Home x64 (20H2) (10 Pro on 2nd pc)
       #3

    Thelps said:
    ...there are 4 'static' MAC addresses listed there as well. I don't recognise these IP addresses or MAC addresses....Perhaps a different way to explain these anomalous addresses?
    There is. They are Multicast addresses and, like the 192.168.***.*** range of IP addresses, are Private address ranges. These are reserved for internal use on your own network only. We all have them...

    Addresses in the range of 224.0.0.0 to 224.0.0.255 are individually assigned by IANA and designated for multicasting on the local subnetwork only...

    The 239.0.0.0/8 range is assigned by RFC 2365 for private use within an organization...
    Multicast address - Wikipedia
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  4. Thelps's Avatar
    Posts : 106
    Windows
    Thread Starter
       #4

    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?
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  5. Bree's Avatar
    Posts : 18,600
    10 Home x64 (20H2) (10 Pro on 2nd pc)
       #5

    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.

    ...the least significant bit of the first octet of a MAC address distinguishes individual addresses from group addresses. That bit is set to 0 in individual addresses and set to 1 in group addresses.
    MAC address - Wikipedia
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  6. Thelps's Avatar
    Posts : 106
    Windows
    Thread Starter
       #6

    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.
      My Computer


 

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