Multicast address
224.0.0.251
224.0.0.251 is in 224.0.0.0/4, the multicast block (RFC 5771). It isn't routed on the public internet, so there's nothing public to look up. The mDNS group, where devices announce names ending in .local (Apple's Bonjour, printers, smart speakers).
At a glance
- Block
- 224.0.0.0/4
- Defined in
- RFC 5771
- On the public internet
- No
About this block
A multicast address names a group, not a device: one packet sent to it reaches every receiver that has joined. IPv4 multicast is 224.0.0.0/4, and IPv6's is ff00::/8.
Where you'll see it
- Local network discovery: mDNS (Bonjour) at 224.0.0.251 and ff02::fb, and SSDP/UPnP at 239.255.255.250.
- IPTV and other streams that ISPs send to many homes at once.