On 3/8/24 18:35, George at Clug wrote:
Thanks for your comments, Tomas and Jeremy.
George
On Saturday, 03-08-2024 at 19:43 jeremy ardley wrote:
On 3/8/24 17:26, [email protected] wrote:
It is not/for/ multicast IP, it/uses/ multicast for name resolution.
In a nutshell [1], it sends a "DNS" request to the local network asking
"who is called Fritz here?", and Fritz answers with its IP. So sys-non-
admins don't have to set up a name server.
To amplify on that, it is used in situations where there is no DHCP server.
IPv4 clients will then automatically assign themselves an address from
169.254.X.X/16 range (X.X is derived from the MAC address)
They then multicast their hostname and IP address to everyone else on
the LAN using mDNS.
It is not a Microsoft only standard. It is defined in RFC 3927, "Dynamic
Configuration of IPv4 Link-Local Addresses."
It is used on a wide variety of hosts including Linux.
Further info: The multicast for mDNS does not use the 169.254 range but
instead uses the multicast address 224.0.0.251 and port 5353.
So every host with a 169.254.x.x address will also listen on port
224.0.0.251:5353 to get hostname and IP addresses of similar hosts on
the LAN.
NB. Multicast is usually restricted to a single LAN unless the network
administrators enable multicast routing on the routers or switches
joining LAN segments. As a result, the 168.254.x.x scheme usually only
works on a single LAN
