On Mon, May 22, 2023 at 08:26:47PM -0400, Dan Ritter wrote: > Tom Reed wrote: > > > > > > > > If I know the network addr: 192.168.1.0 > > And know the broadcast addr: 192.168.1.255 > > Then I should have the possibility to cal the netmask addr: 255.255.255.0 > > > > Isn't it? > > > No. What's the netmask if you have: > > IP: 192.168.255.132 > broadcast: 192.168.255.255 ?
See my other post: I think Tom means the "subnet address", which by convention is the "subnet address" in the sense of [1]. I don't know whether there is an accepted RFC for that, but it seems to be current practice (there are proposals to get rid of that one [2], which actually doesn't make any sense, but IPv6 would be the better way to go anyway :) I see Greg and you interpreted Tom's "net addr" as "the internet address of the host in question". I think it's meant as the "subnet address" in the sense of [1]. It seems a relic from BSD, which seems to have used it /also/ as broadcast. These days it is a disfunctional appendage mainly used to torture networking students, but it's there with a big sign "DON'T STEP ON IT" ;-) Cheers [1] https://en.wikipedia.org/wiki/IPv4#First_and_last_subnet_addresses [2] https://www.ietf.org/archive/id/draft-intarea-schoen-lowest-address-00.html -- t
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