❦ 29 décembre 2016 12:24 -0800, Russ Allbery <rra@debian.org> : > No, I'm not talking about CIDR notation, which of course is long-standing > and familiar. I'm talking about randomly appending a CIDR suffix to > something that is obviously *not* the base for that CIDR block. > > In other words, 192.168.0.0/24 is fine. The problem is with deciding to > merge two completely different things (a CIDR network specification, and > an individual IP address) in this weird hybrid notation that, by RFC 4632, > would mean the network starting at 192.168.0.195 and extending for a /24. > Which is a nonsensical specification. > > IIRC, this was done in ip to "save space" instead of using the natural > expression, namely: > > 192.168.0.195 net 192.168.0.0/24 > > Saving space in UI output intended for humans by introducing new notation > is almost never a good idea. > > It's possible that some other tool has abused CIDR notation in this way, > but ip is still the only place I ever see it. It's definitely not common. It's quite common. For example, on JunOS, this is also how IP addresses are expressed. This is quite like "192.168.0.195 netmask 255.255.255.0", except this is "192.168.0.195 prefixlen 24" which then can be abbrieviated to "192.168.0.195/24". You know this is not a prefix because the prefix is "192.168.0.0/24" (and the prefix length is less than 31). This is also how it works with IPv6 (even on Cisco). -- Extreme fear can neither fight nor fly. -- William Shakespeare, "The Rape of Lucrece"
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