On 15/11/2020 21:14, HamApps Support (VK3AMA) wrote:
as I explained off list, 220.127.116.11 is a special multicast address known as the "All Hosts" address. The 18.104.22.168/8 block of addresses is also special as they are never routed. 22.214.171.124 specifically (not just any 126.96.36.199/8 address) will work with the current JTAlert because every host joins that multicast group, on every network interface, automatically without the recipient application requesting membership. 188.8.131.52, the "All Hosts" multicast address, is just one member of the 184.108.40.206/24 block of 255 multicast addresses.
I think there may be some fundamental misunderstanding here about IPv4 address notation. IPv4 addresses are 32-bit numbers which are often written as a group of 4 decimal octets (representing 8-bits each), known as dotted decimal notation. IPv4 addresses are also written as groups, or subnets, where a specified number of high order bits, the prefix, are fixed and the remaining lower order bits form he membership of the subnet group. Some common subnets are:
127.0.0.0/8 - the loop-back addresses (they all start with 127., yes >16 million of them!), of which 127.0.0.1 is the most commonly used and supported.
192.168.0.0/16 - the class C private address block, they all start with 192.168. and are not normally routed.
172.16.0.0/12 - the class B private address block, they are 172.16.0.0 thru 172.31.255.255, also not normally routed.
10.0.0.0/8 - the class A private address block, they all start with 10., also not normally routed.
220.127.116.11/4 - the multicast group addresses, they are 18.104.22.168 thru 22.214.171.124.
Multicast group addresses are further subdivided, including
126.96.36.199/8 (not routed), and 188.8.131.52/24 (routing scope
determined by further subdivisions and router settings, a.k.a.