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What are the purposes of the addresses in this ARP table?

I notice that ANY computer that I go to, if I do a arp -a command from a command line, I receive a reply back of 224.0.0.22. It returns as a physical address and is labeled as static. I get this from work computers, home computers, everywhere! So what is it exactly for? Where does it point to?

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marked as duplicate by Ƭᴇcʜιᴇ007, Doug Harris, avirk, slhck, Nifle Jun 27 '12 at 10:09

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3 Answers 3

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224.0.0.22 is a multicast-address.

Multicast is thought for ip addresses which can be "subscribed" to. A multicast IP can be subscribed to by multiple network interfaces and will be routed by routers in a special way. This way you can create an IP address with multiple recipients.

An example would be a peer to peer chat where everybody, instead of sending a message to every other computer, send them to the multicast address where the routers take over the work of distributing the data to all the correct addresses.

Another unlikely real world example: Let's say there's a special "copy" mailing address registered in the post office. All mail sent to this address will be opened, all pages copied and sent to 5 different addresses.

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The address 224.0.0.22 is used for the IGMPv3 protocol.

This protocol is used by hosts to manage its multicast insterests. You can have more information on the Wikipedia page linked above.

The address 01:00:5e:00:00:16 is the correspondent layer 2 address. You can read here and here about how multicast ip addresses are converted to MAC multicast addresses. And you can use this tool if you want to try it.

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Sory. My first answer was wrong since I've read 224.0.0.2 instead of 224.0.0.22. –  criziot Jun 26 '12 at 13:50

It is used for IGMPv3 Reporting. See also here (translated from polish)

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