What is the VPC accepted address and why i am trying to create a vpc but the ip i am providing is not accepted which is 192.168.1.1/16 but aws says i can use the following range if i set to 192.168.0.0/16 it works , i guess to an extent still some clarity would be great  When you create a VPC, we recommend that you specify a CIDR block (of /16 or smaller) from the private IPv4 address ranges as specified in RFC 1918:  10.0.0.0 - 10.255.255.255 (10/8 prefix)  172.16.0.0 - 172.31.255.255 (172.16/12 prefix)  192.168.0.0 - 192.168.255.255 (192.168/16 prefix)
What is the recommended CIDR when creating VPC on AWS? I have been creating AWS VPCs and I am wondering if there is a recommended CIDR value when creating VPCs. What are the factors that I must consider when choosing a CIDR and does the CIDR value affect the performance of the network?
How bad is it to use display: none in CSS? I've heard many times that it's bad to use display: none for SEO reasons, as it could be an attempt to push in irrelevant popular keywords. A few questions:   Is that still received wisdom? Does it make a difference if you're only hiding a single word, or perhaps a single character? If you should avoid any use of it, what are the preferred techniques for hiding (in situations where you need it to become visible again on certain conditions)?   Some references I've found so far:       If you're straight-out using CSS to hide text, don't be surprised if that is called spam. I'm not saying that mouseovers or DHTML text or have-a-logo-but-also-have-text is spam; I answered that last one at a conference when I said "imagine how it would look to a visitor, a competitor, or someone checking out a spam report. If you show your company's name and it's Expo Markers instead of an Expo Markers logo, you should be fine. If the text you decide to show is 'Expo Markers cheap online discount buy online Expo Markers sale ...' then I would be more cautious, because that can look bad."   And  on the same article     We can flag text that appears to be hidden using CSS at Google. To date we have not algorithmically removed sites for doing that. We try hard to avoid throwing babies out with bathwater.   Eric Enge      The legitimate use of this technique is so prevalent that I would rarely expect search engines to penalize a site for using the display: none attribute. It’s just very difficult to implement an algorithm that could truly ferret out whether the particular use of display: none is meant to deceive the search engines or not. How does the Southwest Airlines boarding process work? I'm flying this week on Southwest Airlines for the first time. I paid for "Early Bird" automatic checkin and the FAQ mentions something about "A" boarding passes. I have no idea what that means, and I know that Southwest doesn't have assigned seats.  How does the boarding process work and is there anything I should be aware of? Delayed eraser experiment (Kim experiment) Will I receive an interference pattern on D0 detector   if D1, D2, D3, D4 exist in the set up of the experiment, but they are thousands of light years far? Simply, to set up the experiment so that I detect all of the signal photons on D0 before I detect any of idler photons! I need to host several Apache virtual hosts with SSL from a single IP.  Now - I understand that because SSL wraps around the HTTP request, there's no way to know which host is being requested until a public key has been sent to the client first. This essentially breaks the possibility of SSL virtual hosts using a standard SSL certificate.  I have obtained a Unified Communications Certificate (UCC), otherwise known as a Subject Alternative Name (SAN) certificate. This allows me to serve the same certificate for multiple domains.  I would like this to be the certificate served by Apache for any SSL request - and then have Apache resolve the virtual host as usual, once the encryption has been established.  How should I configure Apache for this? I have tried to research how this can be done, but all I can find are quotes which say that it is possible, but no specifics:    wiki.apache.org/httpd/NameBasedSSLVHostsWithSNI     While Apache can renegotiate the SSL   connection later after seeing the   hostname in the request (and does),   that's too late to pick the right   server certificate to use to match the   request hostname during the initial   handshake, resulting in browser   warnings/errors about certificates   having the wrong hostname in them.   serverfault.com/questions/48334/apache-virtual-hosts-with-ssl     Incidentally, it is possible to have   multiple SSL-secured named virtual   hosts on a single IP address - I do it   on my website - but it produces all   sorts of warnings in the Apache logs,   and certificate warnings in the   browser. I certainly wouldn't   recommend it for a production site   that needs to look clean.   -David Jul 31 at 4:58   www.digicert.com/subject-alternative-name.htm     Virtual Host Multiple SSL sites on a single   IP address. Hosting multiple   SSL-enabled sites on a single server   typically requires a unique IP address   per site, but a certificate with   Subject Alternative Names can solve   this problem. Microsoft IIS 6 and   Apache are both able to Virtual Host   HTTPS sites using Unified   Communications SSL, also known as SAN   certificates.     Please help. For what natural numbers is $n^3 < 2^n$? Prove by induction Problem  For what natural numbers is $n^3 &lt; 2^n$?  Attempt @ Solution   For $n=1$, $1 &lt; 2$ Suppose $n^3 &lt; 2^n$ for some $n = k \ge 1$ It looks like the inequality is true for $n = 0$, $n = 1$ and $n\ge10$ But, how can I prove this through induction? Infinite series $\sum _{n=2}^{\infty } \frac{1}{n \log (n)}$ Recently, I encountered a problem about infinite series. So my question is how to know whether the infinite series $\sum _{n=2}^{\infty } \frac{1}{n \log (n)}$ is convergent? How do I change the hostname without a restart? I want to change the OS hostname but I do not want to restart.  I have edited /etc/hostname but it requires a restart to get implemented. How to avoid this? How do I remove Windows but keep Ubuntu? How do I check if an element is hidden in jQuery? Is it possible to toggle the visibility of an element, using the functions .hide(), .show() or .toggle()?  How would you test if an element is visible or hidden? Tracking down where disk space has gone on Linux? Electromagnetic waves can be shielded by a perfect conductor. What about gravitational fields or waves? Are actions and bonus actions interchangeable? How did the Swooping Evil Venom infused rain affect the magical community? I didn't see any wizards drenched in the rain at the end of Fantastic Beasts and Where to Find Them (don't recall, actually). But would the rain equally affect the wizards as it did no-maj's?   This event is something that doesn't necessarily need to be forgotten by the Wizarding community. How would they avoid being obliviated by the rain?  (They could avoid the rain by Apparating, but what about the showers and drinking water?)  This question is picking at my brain. Neural network references (textbooks, online courses) for beginners I want to learn Neural Networks.  I am a Computational Linguist. I know statistical machine learning approaches and can code in Python.   I am looking to start with its concepts, and know one or two popular models which may be useful from a Computational Linguistics perspective.  I browsed the web for reference and found a few books and materials.   Ripley, Brian D. (1996) Pattern Recognition and Neural Networks, Cambridge Bishop, C.M. (1995) Neural Networks for Pattern Recognition, Oxford: Oxford University Press. some links, like ,  (University of Toronto Psychology Department),  (University of Wisconsin Computer Science) and  (Facebook Research).   Coursera courses are generally nice, if anyone knows anything relevant from them. I prefer materials with lucid language and ample examples. Let's re-evaluate the Question Timer I know this seems like a good idea, but this far into the game you should be able to tell from network behavior that I'm not a spammer…  I had a compound question. I broke it up because breaking it up was possible—it probably isn't even necessary in that it wouldn't otherwise get closed. Now I doubt either of my questions will be easily answered, but it stinks when you want to run (irl) to have to wait on a question timer which means posting one at a later time. Can't we fight spammers more effectively in a different way?  You know it's my intent to ask the question (or you'd give me a captcha). You also know that historically my questions have been   Can't we find a way to make this not stupid? Make Windows 10 stop installing driver software automatically Using processing.runandload in QGIS 3 How should I handle possible revenge downvotes? I don't like such kind of questions on Meta, so I will try to make it a good question and describe all with a details.  Today I down-voted  added a comment with explanations why I down-voted it, and flag it as non constructive (my flag was marked as helpful). An hour later  was downvoted, without any comment left about the reason. Yes, that wasn't my best answer, but in my opinion it answers the question. Well, even if somebody considered my answer incorrect he could add the correct answer, or up-vote the competitive ones. I checked the  who made competitve answer, and he didn't get any rep today for that answer.   It was my second down-vote on Stack Overflow, so I was a little bit down, after that. I think who could considered my answer so completely wrong, and that I thought that maybe it was revenge down-vote. So I checked  of the user I down-voted today, and it was clear that he down-voted some answers today. After I checked that that user cast only 19 downvotes in 8 months, so chances were very big that this was revenge down-voting.  I came to this meta, and searched what I should do in this case. I found that most questions about down-votes, were closed as duplicates. After I found , and found that a team member of Stack Exchange suggested to cast a flag for moderator attention, and explain the situation there.  I did that, and create next flag:     I think after I down-voted this question (and a comment about this), the OP down-voted me in revenge; it's clear from his today's reputation and from timing of my down-vote of his question, and time when one of my answers was downvoted. I cannot be 100% sure about that, but if somebody can check this, and point him that it's not the good way to do.   As you can see, I didn't ask for returning any reputation, or banning that user, I just wanted, somebody to point him, that he did wrong. And after I get this respons on my flag: "declined - flags should only be used to make moderators aware of content that requires their intervention." So in the end I also lost 10 points of the flag weight.  After describing all situation in details, I want to know were exactly I was wrong here. And what should I do next time something like this happens? What does this notation mean? $f(x) \equiv A$? If $\lim_{x\rightarrow\infty}f(x) = A$, prove that $f(x)\equiv A$.  Any help would be appreciated! I just don't even understand the question. Air friction at supersonic velocities