224.0.1.1 is a Special Purpose IP Address.

The 224.0.0.0/4 Address Block is allocated for multicast address assignments, formely known as the Class D address space.
[ RFC1112, ^ ] , Host Extensions for IP Multicasting

224.0.1.0/24 - Internetwork Control Block
Addresses in the 224.0.1.0/24, the Internetwork Control Block are used for protocol control traffic that MAY be forwarded through the Internet.
[ RFC5771, ^ ]


224.0.1.1 - NTP Network Time Protocol
References: [ RFC1119, ^ ][ RFC5905, ^ ][David_Mills]

  
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