I'm currently learning about IPv4 and subnetting. As far as I understand, if we want to create 4 small isolated networks with the size 50, we can use subnetting.  If we subnet a Class-C IPv4 network(210.210.210.0) into 4 small networks with the same size (0~63, 64~127, 128~191, 192~255), these small networks are still essential belonged to the big logical network (210.210.210.0) even though we assign subnet masks to them.   If I understand correctly, they can communicate with each other since they share the same network portion. So, in practice, how can we isolate these small networks?  Thanks:)
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This is a  about IPv4 Subnets.      Related:               How does Subnetting Work, and How do you do it by hand or in your head?  Can someone explain both conceptually and with several examples? Server Fault gets lots of subnetting homework questions, so we could use an answer to point them to on Server Fault itself.   If I have a network, how do I figure out how to split it up? If I am given a netmask, how do I know what the network Range is for it? Sometimes there is a slash followed by a number, what is that number? Sometimes there is a subnet mask, but also a wildcard mask, they seem like the same thing but they are different? Someone mentioned something about knowing binary for this?
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I have two OSX machines on a local subnet.  Pings from Machine A to Machine B consistently timeout until Machine B pings Machine A.  After B pings A, A can successfully ping B, but this success is temporary; if there is no communication between the two machines for a half hour or so, pings from A to B begin timing out again (until B pings A again).  How can I ensure that B is always reachable from A, without having to "kickstart" the connection by pinging A from B first?
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While there's a wide variety of private non-routable networks across 192.168/16 or even 10/8, sometimes in being thoughtful of potential conflict, it still occurs. For example, I set up an installation OpenVPN once with the internal VPN network on 192.168.27. This was all fine and dandy until a hotel used that subnet for floor 27 on their wifi.  I re-IP'd the VPN network to a 172.16 network, since that seems to be all but unused by hotels and internet café's. But is that an appropriate solution to the problem?  While I mention OpenVPN, I'd love to hear thoughts about this problem on other VPN deployments, including plain ol' IPSEC.
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Are there dedicated protocols to achieve a private set intersection where one of the set is of small constant size $c$ and the other one of size $n$?  What are the resource complexities of this kind of protocol, in terms of communication and computation?
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35 lines, 55 lines, 100 lines, 300 lines? When you should start to break it apart? I'm asking because I have a function with 60 lines (including comments) and was thinking about breaking it apart.  long_function(){ ... }   into:  small_function_1(){...} small_function_2(){...} small_function_3(){...}   The functions are not going to be used outside of the long_function, making smaller functions means more function calls, etc.  When would you break apart a function into smaller ones? Why?   Methods should do only one logical thing (think about functionality) You should be able to explain the method in a single sentence It should fit into the height of your display Avoid unnecessary overhead (comments that point out the obvious...) Unit testing is easier for small logical functions Check if part of the function can be reused by other classes or methods Avoid excessive inter-class coupling Avoid deeply nested control structures   Thanks everyone for the answers, edit the list and vote for the correct answer I'll choose that one ;)  I am refactoring now with those ideas in mind :)
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I have just asked a question on   I read from this meta answer  that suggested     From a desktop support perspective there are certainly cases where a   large(r) number of machines will be affected by something, in which   case it's appropriate for SF. There are then others that are isolated   to a single computer, these tend to be the ones I vote to move to SU.   Since my question is clearly not about a single computer and is external to a single computer, I turned to ServerFault. I thought the question is about how to replicate a network admin strategy on my own (home) network. My question is, however, marked as off-topic, and I did see that homenetwork questions are off-topic. But this is not a single computer issue either.  My question is:  Where should such home/small network questions be asked?  What's the real difference between "professional" networks and the smaller networks that I build for my home or lab with a handful computers?  -- UPDATE --  The question asked here is different from the said duplicate question  as that question is about the difference among computer science and programming SE sites. It has nothing to do with network administration, whether it's large or small networks. None of the two SE sites in question (Server Fault and Super User) is even mentioned in the question or in the 2 cited answers.  -- UPDATE2 --  This question is not a duplicate of , which was cited in the OP and was the cause of this question. That question does not cover the overlapping area of small networks, which could both be for work and for home network.
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My web server (Ubuntu, Nginx) have both IPv4 and IPv6 addresses assigned by the host. For my website, shall I bind it to only an IPv6 address? Is it the standard recommended way? Or, shall I use both IPv4 and IPv6 addresses?
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I am attempting to set up a web server (nginx) that needs access to the internet while also being hooked up to an ELB but I am having trouble getting this solution working.  Details:   3 public subnets   a b c  3 private subnets   a b c  1 ELB   This has the three public subnets included in its default pool  1 NAT instance in public subnet   The various guides I have found useful for getting the public subnets hooked up to the ELB by pointing the subnets to the IGW.  These set ups do not take in to consideration the need for internet access.  When I change the route table for the single NIC from the IGW to the nat instance I get internet access but I lose the ability to connect to the ELB and visa versa, when I update the route table to use the IGW I lose the ability to connect to the internet.  I can allocate an EIP and give it access that way but was hoping to avoid exposing this server the internet via a public address if possible.  What I am thinking is that I can either 1) add a second NIC to the web servers that need internet access so they have a leg out via a NAT instance and also have a leg in the public subnet to connect to the load balancer or 2) I can use the nat instance as the gateway for my network.  Has anybody set something similar to this up?
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I am trying to split a network. I have an adjacency matrix that shows edges between nodes. The weight of the edge depends upon the total number of overlapping items between two nodes/union of items between two nodes.  Next, I am trying to partition this adjacency matrix into sub-networks that show tightness of these sub-networks based on the strength of the connections within them. Right now I am using Networkx python's modularity metric to do this splitting. I am looking for a second opinion. Also, I can keep splitting until the sub-networks further until there are no more sub-networks left.  In addition to that, I am searching for a metric that can tell me whether further splitting this sub-network gives me better information (aka better tighter sub-network than the last one).FYI, this is an unsupervised approach.  Hope this makes sense. If not please fire away your comments/questions and I will edit my response accordingly. Any help is much appreciated.  Rocky
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I've been looking over some board designs and have been trying to identify the reasons behind using resistor networks over individual resistors. Some guesses I can think of are a reduced part-count and complexity. Does it also follow that a design using a resistor network is cheaper than one that uses individual resistors? Because of this, I would think one would try to maximize use of networks, but many of the designs use several individual resistors instead and I can't figure out why.  And a separate but relevant question: are capacitor networks in the same boat?
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NAT is a wonderful concept used in ipv4. It is the major reason for the existence on internet, in my concerns. There are no networks in the world that doesn't work without employing NAT.  All I seek to know is that, would NAT be required if after ipv6 is implemented, would NAT be eliminated or be used in a different way(Transformed or Upgraded into a new version with some added abilities to tackle any situations or problems that the network specialists or researchers foresee).
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I need a pair of non-isomorphic graphs with the smallest n-vertex possibility and where degree sequences are the same. Is the minimum number 2, such as a multigraph with n=2? Please help with the reasoning on this question. Thank you!
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This is a  about Hosting multiple SSL websites on the same IP.   I was under the impression that each SSL Certificate required it's own unique IP Address/Port combination. But the  is at odds with this claim.  Using information from that Question, I was able to get multiple SSL certificates to work on the same IP address and on port 443. I am very confused as to why this works given the assumption above and reinforced by others that each SSL domain website on the same server requires its own IP/Port.  I am suspicious that I did something wrong.  Can multiple SSL Certificates be used this way?
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Three server A,B &amp; C. How to ssh connect from A to C via intermediate server B, if A to B &amp; C to B are password less(key)? I encountered this in an interview. Anyone knows how?
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If I enter for example "block 59.164.0.0/20" as a firewall rule.  Does that mean it blocks the IPs 59.164.0.0 to 59.164.0.20 or does it mean something else ?
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I thought the Ethernet is logically a one-line communication bus (for argument's sake, I am excluding hubs). All machines attached on the bus hears the same signals and the machines themselves try to avoid collisions by randomly backing off.    If so, why would splitting one Ethernet line from my home router into two and connecting two computers not work? Why do I have to add a switch to it?  What the Internet said would not work.                                                             +----------+                                                +----------&gt;|computer 1|                                                |           +----------+     +------------------+       +---------------+     |4 port home router+------&gt;|simple splitter|     +------------------+       +---------------+                                                |           +----------+                                                +----------&gt;|computer 2|                                                            +----------+   What the Internet said I should do                                                             +----------+                                                +----------&gt;|computer 1|                                                |           +----------+     +------------------+       +---------------+     |4 port home router+------&gt;|    switch     |     +------------------+       +---------------+                                                |           +----------+                                                +----------&gt;|computer 2|                                                            +----------+   Is this because of the signal degradation (reduced electric current)?    Thank you for all the answers! The reason why I did not just use the two ports of my home router is...  The 4-port gigabit router is in my room, and I had put a computer in another room (also my room, though). Since a wired network is far more reliable and secure, I had bought a long Ethernet cable and and connected the computer to the router. Now I was thinking about adding another computer to that room. I could buy another long Ethernet cable, but then there will be two cables between the rooms. The one line already is a minor annoyance, so I thought if I could share the one line between the two computers in that room. A switch would work, but it requires power and is a little bit pricey. That is why I wondered why it would not work to simply split the physical Ethernet cable.  Apparently I do not completely understand how Ethernet and a switch work. I just have some bit of knowledge I heard in my college class.
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Preface: I'd like to avoid the question of whether one should run data and power together; my question is focused on Code compliance.  I'm trying to ensure I interpret Code correctly when running Cat 5/6 cabling and power together in the same conduit.  For starters, I understand that nothing in Code prohibits one from doing this; I'm trying to ensure I understand how to do it properly.  I'm wiring a basement office for power and data, and I'll be running the electrical in EMT.  My plan was to pull THHN for the power rather than pull NM-B, but then 800.133(2) Exception 1 made me scratch my head.  Is my understanding of the Article that if I want to run both data (Cat6) and power in the same conduit, that the power needs to be sheathed (i.e. NM-B).  Is it unacceptable to pull individual THHN conductors and the Cat6 together in the same conduit?     800.133 2) Other Applications. Communications wires and cables shall be separated at least 50 mm (2 in.) from conductors of any electric   light, power, Class 1, non–power-limited fire alarm, or medium-power   network-powered broadband communications circuits.      Exception No. 1: Where either (1) all of the conductors of the   electric light, power, Class 1, non–power-limited fire alarm, and   medium-power network-powered broadband communications circuits are in   a raceway or in metal-sheathed, metal-clad, nonmetallic-sheathed, Type   AC, or Type UF cables, or (2) all of the conductors of communications   circuits are encased in raceway.