5 ms·
> Something I never understood is why people choose 192.168.1.1 for private networks While interviewing someone for an entry-level job, I told the interviewee
by forapurpose 8y ago
> Something I never understood is why people choose 192.168.1.1 for private networks
While interviewing someone for an entry-level job, I told the interviewee that there was a network using 10.0/16 (a 16-bit subnet mask, or more popularly 10.0.x.x). He corrected me and said that 10.0.0.0 networks should have an 8 bit subnet mask (10.x.x.x). On one hand, I definitely liked that he was willing to challenge me, even during an interview, and that he knew the spec (RFC 1918 does assign an 8-bit mask to the 10. private network). On the other hand, I wasn't sure he was technically correct that a 16-bit mask was wrong, even if 8-bits was 'correct', and I couldn't see what negative consequence the 16-bit subnet had - his thinking seemed a bit rigid. Anyway, maybe there are other purists who believe smaller networks should use 192.168/16, or maybe they instinctively use it because the RFC gives it the smaller network allocation. Or maybe they know something that I don't.
> isn't 10.1.1.1 easier to type and more "aesthetically pleasant"?
And it's much easier for non-technical people to understand and to remember without error. In fact, I recommend something even easier, such as 10.9.8.x. For people supporting the non-technical, those little details can save hours, even a day. I've seen cases where after hours of frustration, the support tech discovers that the user typed in something like 129.168, or 192.16.8. Great support reps are great humanitarians, able to handle those situations with grace, without humiliating the poor user, and without heavy drinking.
EDIT: clarifying edit
- y4mi 8y agoHe was wrong. Subnets exits for two things. Physical segmentation of networks and consequently limiting the scope of broadcasts. With a /8 (especially with desktop machines) the broadcast would definitely be a major bottleneck in the network.
- srj 8y ago10/8 is a class A range (high order bit = 0), but CIDR says that you can separately describe which bits are for the network. Unless this interview was conducted more than 20 years ago I'd say your interviewer was mistaken.
- forapurpose 8y ago> I'd say your interviewer was mistaken Is that what you meant to say? The interviewer (me) thought that 10.0/16 was fine, which I think agrees with your analysis. The interviewee said only 10/8 was correct. (Re-reading my GP comment I realize that my role might have been ambiguous, so I've clarified it.)
- HighPlainsDrftr 8y agoIf you said 10/24, I'd immediately think 10.0.0.0/24. 10/8 would certainly be valid. 10.0/16 is too. I remember when CIDR came around back in the 90's. Man people were pissed off when you would call out a 'Class A/B/C/D/E' block. I prefer to always be specific when writing my CIDR. I understand when people don't do it. Be liberal in what you accept and conservative in what you send.
- forapurpose 8y agoYes, Postel's advice applies to many things. I think there is some misunderstanding. The question wasn't the notation but the subnetting. See the story in the GGP.
- srj 8y agoSorry yes, you were right in saying 10.0/16.
- 6t6t6t6 8y ago10.0.0.0/8 is correct, you can only use the last 24 bits. But nothing prevents you from breaking this class A in smaller networks! That means that you can not use 10.0.0.0/7 (which would include 11.0.0.0) but you can use 10.0.0.32/30, that includes from 10.0.0.32 until 10.0.0.35.
- tinus_hn 8y agoFor some reason courses that cover some networking used to make a huge point about the network classes for many years after CIDR made them completely irrelevant.