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Could someone explain what the following IP addresses in my network I found on Terminal via the arp -a command:

224.0.0.251 at 1:0:5e:0:0:fb on en0 ifscope permanent [ethernet]

239.255.255.250 at 1:0:5e:7f:ff:fa on en0 ifscope permanent [ethernet]

Through a Google search I was able to see that they are multicast IP addresses, but still don't know what they are or how they got onto my network. Is this normal and does it happen automatically? Does it pose an issue?

I have a MacBook Pro running Ventura.

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As you have discovered they are multicast addresses for the LAN your Mac connects to. They are used for other devices on your network to discover services on your Mac.

  • 224.0.0.251 is for Multicast DNS, used by discovery protocols like Zeroconf, Bonjour
  • 239.255.255.250 is used by the Simple Service Discovery Protocol

They are not routable, so traffic never leaves the LAN. So, normal to have them, and no risk.

https://en.wikipedia.org/wiki/Multicast_DNS https://en.wikipedia.org/wiki/Simple_Service_Discovery_Protocol

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