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• Google Public DNS is not used in trace route

  - by IT researcher

  In my PC i am using google public DNS as DNS server.In Internet protocol(TCP/IP) properties i have set Preferred DNS server as 8 8 4 4 and Alternate DNS server as 8 8 8 8. According to me this DNS server should be used to resolve any request to website to its IP by using this DNS servers.(see google DNS and How Domain Name Servers Work). But when i checked trace route to a website in my PC i got following Tracing route to www.google.com [74.125.236.80] over a maximum of 30 hops: 1 <1 ms <1 ms <1 ms 192.168.1.201 2 360 ms 349 ms 292 ms 122.178.216.1 3 145 ms 107 ms 148 ms 122.166.32.121 4 32 ms 53 ms 120 ms 122.166.32.9 5 45 ms 42 ms 121 ms 122.175.255.29 6 63 ms 76 ms 51 ms 182.79.255.45 7 52 ms 134 ms 61 ms 72.14.194.22 8 86 ms 59 ms 72 ms 72.14.232.202 9 106 ms 107 ms 60 ms 66.249.94.39 10 101 ms 103 ms 117 ms 209.85.249.235 11 148 ms 224 ms 276 ms 74.125.236.80 Trace complete. When i checked all these IP in who.is i found that it is of my ISP. So my question is where does Google public DNS is used? Also how come my ISP's nameserver is used even if i set google public dns as my dns server in my PC?(OR does my any settings are wrong)

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• Installation of Active Directory on separate VM from DNS does not entierly work - not sure why

  - by René Kåbis

  Not sure what I am doing wrong here. I have a moderately midrange server (16 cores, 2Ghz, 32GB ECC REG RAM, 6TB storage, nothing too extreme) where I am running Hyper-V (Server 2012 R2 Enterprise) in order to provision virtual machines. So why an AD separate from DNS? I want redundancy. I want to be able to move VMs and back them up individually and not have too many services on any one VM. I have already provisioned a VM with DNS, and have set it up right -- essentially, I have: Set up Static IP’s for everyone involved. Installed the DNS service on the DNS VM. Created a forward lookup zone and a reverse lookup zone (primary zone) xyz.ca Configured the zones to use nonsecure and secure dynamic updates (i will change this to secure later after the domain controller is online). Created a A record for the DC in the forward lookup zone (and a reverse ptr) Changed DC’s DNS server (network settings) to the new DNS server. Checked that I can ping the dns server from the new DC by hostname. When I went ahead and did a DCpromo on the DC, and un-cheked the “install DNS” option, everything seemed to go well (no error messages), but I saw no changes on the DNS server whatsoever (no additional settings). Plus, the DNS server seems to be unable to join the domain, as it claims that the domain is not discoverable. As a final note, I do run Symantec Endpoint Protection, which includes a firewall and most settings set as default. I have not yet tried turning this off, but my experience has been that if a service would open up a port on a Windows firewall, it would do the same through Symantec. There is pretty tight integration these days with corporate-class AV and Windows. I have a template vhdx fully set up (just short of any special roles and features) that I can use to replace the current AD VM with, so doing this all over again is not too much skin off of my nose.

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• Avoiding DNS timeouts when a dns server fails

  - by Neil Katin

  We have a small datacenter with about a hundred hosts pointing to 3 internal dns servers (bind 9). Our problem comes when one of the internal dns servers becomes unavailable. At that point all the clients that point to that server start performing very slowly. The problem seems to be that the stock linux resolver doesn't really have the concept of "failing over" to a different dns server. You can adjust the timeout and number of retries it uses, (and set rotate so it will work through the list), but no matter what settings one uses our services perform much more slowly if a primary dns server becomes unavailable. At the moment this is one of the largest sources of service disruptions for us. My ideal answer would be something like "RTFM: tweak /etc/resolv.conf like this...", but if that's an option I haven't seen it. I was wondering how other folks handled this issue? I can see 3 possible types of solutions: Use linux-ha/Pacemaker and failover ips (so the dns IP VIPs are "always" available). Alas, we don't have a good fencing infrastructure, and without fencing pacemaker doesn't work very well (in my experience Pacemaker lowers availability without fencing). Run a local dns server on each node, and have resolv.conf point to localhost. This would work, but it would give us a lot more services to monitor and manage. Run a local cache on each node. Folks seem to consider nscd "broken", but dnrd seems to have the right feature set: it marks dns servers as up or down, and won't use 'down' dns servers. Any-casting seems to work only at the ip routing level, and depends on route updates for server failure. Multi-casting seemed like it would be a perfect answer, but bind does not support broadcasting or multi-casting, and the docs I could find seem to suggest that multicast dns is more aimed at service discovery and auto-configuration rather than regular dns resolving. Am I missing an obvious solution?

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• Internal/external DNS with subdomains

  - by ScottMcGready

  I've got an internal DNS server (part of OS X server) and it's acting as the main DNS server for a specific (physical) site. When it can't resolve hostnames itself, it forwards requests to Google's DNS servers. Everything works well apart from a couple of issues, which I think may be related but can't get to the bottom of. I've got a number of intranet sites setup, that people can access by going to something like: intranet.mydomainname.com selfservice.mydomainname.com These point to various servers in the building that host these sites. Whether internal or external (without VPN), I can access these sites just dandy. Where the issue comes is when I want to host, say, test.mydomainname.com on an external server it fails to resolve as the primary zone for mydomainname.com is internal. How can I get it to look up Google's DNS (or an external one) for that zone if it's not in the list? I've tried everything I can think (adding my host's nameservers etc) of but nothing seems to work fully. Also I can't access intranet sites when connected via VPN and from what I can gather - I believe this might be related to the DNS issue but just wanted to give as much information as possible. Edit The domain mydomainname.com is hosted externally and pointed at the site's public IP. From there we can forward the requests to the relevant internal server. Externally everything works, internally though any subdomain of mydomainname.com is served locally, I want it to be served from Google's DNS / externally. DNS Configuration As per a request, here's the current DNS configuration (OS X server's DNS tab). I've blurred out the .private address as it's not really relevant but it's the server's name. The colored dots are just there to link everything together. Screenshot: In an attempt to clarify this is what I want: intranet.mydomain.com -> 192.168.0.12 selfservice.mydomain.com -> 192.168.0.13 *.mydomain.com -> forward to external DNS mydomain.com -> forward to external DNS At the moment any subdomain of mydomain.com is not forwarded on (think this is because of the primary zone being mydomain.com with a NS of intranet.mydomain.com but could do with a little nod in the right direction.

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• Economical DNS hosting separate from local registrar for country specific TLDs - email or web hosting not required

  - by Eric Nguyen

  Our company owns many country specific top level domains (TLDs; .sg, .my). We will purchase more for other countries in all South East Asia. These domains are associated with our websites hosted on Amazon EC2. The DNS records are currently hosted on a dedicated server that will shut down tomorrow. (The name servers are set to the ones of a web hosting company) Therefore, I will need to host the DNS records somewhere else. Hosting the DNS records with the local registrar costs SGD18 a year per domain in addition to the domain price (which is already very expensive but we have no choice). It would be convenience to host DNS recors for all the country specific TLDs we have using a single service, separate from the local registrars from which we bought the domains. A few searches prompted examples like Amazon Route 53 and dnsmadeeasy.com and the likes. However, since I'm only concern about the country specific TLDs, not .com 1) Is it really economical to host DNS records of all domains in 1 single place as described above? (Have the relevant countries and/or the local registrars done something to keep their monopoly and always charges ridiculous prices for their country specific TLDs?) 2) I would imagine I will need to tell the local registrars to update the name servers to those of the DNS hosting service provider e.g. dnsmadeeasy.com here. Am I correct about how it works here? 3) Will I be able point the TLDs themselves to IP addresses I desire (the EC2 instances where my websites are) or will I only able to do so with the subdomains? 4) Are there any drawbacks that I should know here? Background about our needs: We need the websites associated with the country TLDs to be up and running all the times Also, we'll need to be able to add/edit A and CNAME records We use Google Apps for Business for internal email so I will need to be able to add/edit MX records and TXT records

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• Functional Programming - Lots of emphasis on recursion, why?

  - by peakit

  I am getting introduced to Functional Programming [FP] (using Scala). One thing that is coming out from my initial learnings is that FPs rely heavily on recursion. And also it seems like, in pure FPs the only way to do iterative stuff is by writing recursive functions. And because of the heavy usage of recursion seems the next thing that FPs had to worry about were StackoverflowExceptions typically due to long winding recursive calls. This was tackled by introducing some optimizations (tail recursion related optimizations in maintenance of stackframes and @tailrec annotation from Scala v2.8 onwards) Can someone please enlighten me why recursion is so important to functional programming paradigm? Is there something in the specifications of functional programming languages which gets "violated" if we do stuff iteratively? If yes, then I am keen to know that as well. PS: Note that I am newbie to functional programming so feel free to point me to existing resources if they explain/answer my question. Also I do understand that Scala in particular provides support for doing iterative stuff as well.

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• Tail recursion in C++

  - by Phenom

  Can someone show me a simple tail-recursive function in C++? Why is tail recursion better, if it even is? What other kinds of recursion are there besides tail recursion?

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• What do I change in my domain name's DNS if I get a new Internet provider?

  - by johnny

  My company is about to get a new physical connection to the Internet, replacing the old provider. They, of course, are giving us the allotted IPs, Gateway, and DNS servers. My domain name is registered with a provider like Bluehost, GoDaddy, etc. When this new connection goes in, what do I change in the domain name providers DNS? I know to change what Host point to. That is my new IP address. But what about the name servers? I am confused because the company gave me IP addresses for the name servers, but at the provider is has a DNS server name like ns1.somedomain.com. Also, How do I update the Internet's DNS servers? Thanks.

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• Dynamic DNS at freedns.afraid.org using a Fritz!Box

  - by kai

  I am having some trouble setting up Dynamic DNS with my Fritz!Box 7360. I have set up the Dynamic DNS page with (this is translated from German, so might be worded a bit differently): [x] Use dynamic DNS Dynamic DNS Provider: User defined Update-URL: https://freedns.afraid.org/dynamic/update.php?MY-DIRECT-URL-KEY Domain Name: mydomain.crabdance.com User Name: myusername Password: mypassword Now on the FritzBox status page, it says: Dynamic DNS: activated, mydomain.crabdance.com, Status: Account temprarily deactivated When I check back on http://freedns.afraid.org, my IP address never changes. Is there any way to fix this? Note my router is on an IPv6 network (m-net), with IPv4 only through DS-Lite. I'm not sure whether this affects anything. Update: Following the guide here (putting myusername instead of MY-DIRECT-URL-KEY) hasn't given any succes. However, the status field has changed slightly: Dynamic DNS: activated, mydomain.crabdance.com, Status: unknown

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• Reliable cheap or free DNS service?

  - by superwormy

  I'm looking for a reliable free or cheap DNS service. I've used FreeDNS at FreeDNS.Afraid.org in the past, but it doesn't always seem reliable... sometimes people say they can't access my website (sometimes I can't access it either) by domain name, and yet if I type in the IP address it works fine, so I assume it's some sort of DNS problem. Are there any other cheap or free DNS services out there? I need something reliable that I can manage via a web interface (or scripts if they have an API) that I can use to manage the DNS for ~100 domain names. EDIT: To be clear, I'm looking for DNS hosting, not DNS servers to use for my WAN connection.

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• Point dns server to root dns servers [duplicate]

  - by Dhaksh

  This question already has an answer here: What is a glue record? 3 answers Why does DNS work the way it does? 4 answers I have setup a custom authoritative only DNS server using bind9. Its a Master ans Slave method. Assume DNS Servers are: ns1.customdnsserver.com [192.168.91.129] ==> Master ns2.customdnsserver.com [192.168.91.130] ==> Slave Now i will host few shared hosting websites in my own web server. Where i will link above Nameservers to my domains in shared hosting. My Question is: How do i tell root DNS servers about my own authoritative only DNS server? So that when someone queries for domain www.example.com and if the domain's website is hosted in my shared hosting i want root servers to point the query to my own DNS Server so that the www.example.com get resolved for IP address.

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• precise dns problems after upgrading from lucid

  - by Jazzist

  I am having DNS problems since upgrading to Precise from Lucid yesterday. DNS sometimes works but is very slow. These problems are just like others are having but I'm wondering if someone can help as I have slightly different specifics. I have read this "I really don’t want a local resolver, how can I turn it off? To turn off dnsmasq in Network Manager, you need to edit /etc/NetworkManager/NetworkManager.conf and comment the “dns=dnsmasq” line (put a # in front of it) then do a “sudo restart network-manager”." I do not have this line to comment. Checking in Synaptic Package Manager reveals that dnsmasq isn't install (dnsmasq-base is). Editing / creating connections using network manager GUI (and specifying DNS servers) doesn't help; ubuntu is not respecting user GUI set DNS servers. Should these GUI tools not work? "I use static IP configuration, where should I put my DNS configuration? The DNS configuration for a static interface should go as “dns-nameservers”, “dns-search” and “dns-domain” entries added to the interface in /etc/network/interfaces" Are any examples of this available? My /etc/network/interfaces is extremely sparse. For now I have edited /etc/resolv.conf replacing nameserver 127.0.0.1 with that of my DNS server (my broadband router), but I don't know how long this fix will last before the file is overwritten by this new system (dnsmasq?).

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• Implement DNS filtering

  - by Michele

  I was wondering what would be the best way to implement DNS filterting. The scenario is this: we need to setup two custom DNS servers to use on our company's computers so that we can filter DNS requests for certain domains and return custom IPs and forward other requests to our ISPs DNS servers. We were thinking about using either PowerDNS or MyDNS because they support MySQL out of the box and we need to change the list of domains to filter quite often. Thanks a lot for your help! :)

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• Creating reverse DNS entries which resolve [closed]

  - by Tiffany Walker

  Possible Duplicate: Reverse DNS - how to correctly configure for SMTP delivery I ran a DNS check and ended up with the following error: FAIL: Found reverse DNS entries which don't resolves IP-IP-IP-IP.HOST.DOMAIN.TLD ? ??? All IP's reverse DNS entries should resolve back to IP address (MX record's name -> IP -> IP Reverse -> IP). Many mail servers are configured to reject e-mails from IPs with inconsistent reverse DNS configuration. How do I properly configure and it so it goes to an IP?

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• How to change from own Internal/Extrernal DNS to use an outsourced service like DNS Made Easy?

  - by Joakim

  Our current setup is a co-located linux box with an openvz kernel with a handful virtual containers for www, mail etc. and one container run Bind9 with a split views configuration serving External and Internal DNS. The HW-Node runs a shorewall firewall and all containers uses private ip's. The box (and DNS) basically handles web and mail for a handful domains and it works well but we still think it would be a good idea to outsource the public DNS and now to my question... Although I am fairly comfortable with the server stuff and DNS, I'm far from a pro and guess I basically need some confirmation that I am thinking in the right direction in that I basically just move the content of our external view (with zone files) to the external service and keep the internal view (or actually remove the view), update the new external DNS with thier names servers, update the info at my registrar and wait for propagation or have I missed something? Maybe someone else here run something similar already and can share some exteriences? I found this question which at least confirms it can be done.

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• OpenVPN Push DNS Not Working Correctly On Windows

  - by woodsbw

  I currently have OpenVPN server setup on an Ubuntu machine, as well as DNSMasq. I am wanting to push DNS to the client (road warrior setup.) I had the push "dhcp-option DNS x.x.x.x" where x.x.x.x was an open OpenDNS server, for testing, and everything was working when I connected from my Windows client But now that I have DNSMasq setup, and I changed the "dhcp-option DNS x.x.x.x" to the DNSMasq server, but when they client connects it still receives the old, OpenDNS DNS server IP. I'm at a bit of a loss here, I have tried flushing DNS on the client, rebooting the server, and I even grep'd the entire server to see if the OpenDNS IP was in some other config I was missing...it wasn't. One other note, when connect to the VPN and explicitly run nslookup against against the DNSMasq IP, the addresses resolve correctly, so it isn't a DNSMasq issue.

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• VPN Connection causes DNS to use wrong DNS server

  - by Bryan

  I have a Windows 7 PC on our company network (which is a member of our Active Directory). Everything works fine until I open a VPN connection to a customer's site. When I do connect, I lose network access to shares on the network, including directories such as 'Application Data' that we have a folder redirection policy for. As you can imagine, this makes working on the PC very difficult, as desktop shortcuts stop working, software stops working properly due to having 'Application Data' pulled from under it. Our network is routed (10.58.5.0/24), with other local subnets existing within the scope of 10.58.0.0/16. The remote network is on 192.168.0.0/24. I've tracked the issue down to being DNS related. As soon as I open the VPN tunnel, all my DNS traffic goes via the remote network, which explains the loss of local resources, but my question is, how can I force local DNS queries to go to our local DNS servers rather than our customers? The output of ipconfig /all when not connected to the VPN is below: Windows IP Configuration Host Name . . . . . . . . . . . . : 7k5xy4j Primary Dns Suffix . . . . . . . : mydomain.local Node Type . . . . . . . . . . . . : Hybrid IP Routing Enabled. . . . . . . . : No WINS Proxy Enabled. . . . . . . . : No DNS Suffix Search List. . . . . . : mydomain.local Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : mydomain.local Description . . . . . . . . . . . : Broadcom NetLink (TM) Gigabit Ethernet Physical Address. . . . . . . . . : F0-4D-A2-DB-3B-CA DHCP Enabled. . . . . . . . . . . : Yes Autoconfiguration Enabled . . . . : Yes Link-local IPv6 Address . . . . . : fe80::9457:c5e0:6f10:b298%10(Preferred) IPv4 Address. . . . . . . . . . . : 10.58.5.89(Preferred) Subnet Mask . . . . . . . . . . . : 255.255.255.0 Lease Obtained. . . . . . . . . . : 31 January 2012 15:55:47 Lease Expires . . . . . . . . . . : 10 February 2012 10:11:30 Default Gateway . . . . . . . . . : 10.58.5.1 DHCP Server . . . . . . . . . . . : 10.58.3.32 DHCPv6 IAID . . . . . . . . . . . : 250629538 DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-14-AC-76-2D-F0-4D-A2-DB-3B-CA DNS Servers . . . . . . . . . . . : 10.58.3.32 10.58.3.33 NetBIOS over Tcpip. . . . . . . . : Enabled This is the output of the same command with the VPN tunnel connected: Windows IP Configuration Host Name . . . . . . . . . . . . : 7k5xy4j Primary Dns Suffix . . . . . . . : mydomain.local Node Type . . . . . . . . . . . . : Hybrid IP Routing Enabled. . . . . . . . : No WINS Proxy Enabled. . . . . . . . : No DNS Suffix Search List. . . . . . : mydomain.local PPP adapter Customer Domain: Connection-specific DNS Suffix . : customerdomain.com Description . . . . . . . . . . . : CustomerDomain Physical Address. . . . . . . . . : DHCP Enabled. . . . . . . . . . . : No Autoconfiguration Enabled . . . . : Yes IPv4 Address. . . . . . . . . . . : 192.168.0.85(Preferred) Subnet Mask . . . . . . . . . . . : 255.255.255.255 Default Gateway . . . . . . . . . : DNS Servers . . . . . . . . . . . : 192.168.0.16 192.168.0.17 Primary WINS Server . . . . . . . : 192.168.0.17 NetBIOS over Tcpip. . . . . . . . : Disabled Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : mydomain.local Description . . . . . . . . . . . : Broadcom NetLink (TM) Gigabit Ethernet Physical Address. . . . . . . . . : F0-4D-A2-DB-3B-CA DHCP Enabled. . . . . . . . . . . : Yes Autoconfiguration Enabled . . . . : Yes Link-local IPv6 Address . . . . . : fe80::9457:c5e0:6f10:b298%10(Preferred) IPv4 Address. . . . . . . . . . . : 10.58.5.89(Preferred) Subnet Mask . . . . . . . . . . . : 255.255.255.0 Lease Obtained. . . . . . . . . . : 31 January 2012 15:55:47 Lease Expires . . . . . . . . . . : 10 February 2012 10:11:30 Default Gateway . . . . . . . . . : 10.58.5.1 DHCP Server . . . . . . . . . . . : 10.58.3.32 DHCPv6 IAID . . . . . . . . . . . : 250629538 DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-14-AC-76-2D-F0-4D-A2-DB-3B-CA DNS Servers . . . . . . . . . . . : 10.58.3.32 10.58.3.33 NetBIOS over Tcpip. . . . . . . . : Enabled Routing table Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 10.58.5.1 10.58.5.89 20 10.58.5.0 255.255.255.0 On-link 10.58.5.89 276 10.58.5.89 255.255.255.255 On-link 10.58.5.89 276 10.58.5.255 255.255.255.255 On-link 10.58.5.89 276 91.194.153.42 255.255.255.255 10.58.5.1 10.58.5.89 21 127.0.0.0 255.0.0.0 On-link 127.0.0.1 306 127.0.0.1 255.255.255.255 On-link 127.0.0.1 306 127.255.255.255 255.255.255.255 On-link 127.0.0.1 306 192.168.0.0 255.255.255.0 192.168.0.95 192.168.0.85 21 192.168.0.85 255.255.255.255 On-link 192.168.0.85 276 224.0.0.0 240.0.0.0 On-link 127.0.0.1 306 224.0.0.0 240.0.0.0 On-link 10.58.5.89 276 224.0.0.0 240.0.0.0 On-link 192.168.0.85 276 255.255.255.255 255.255.255.255 On-link 127.0.0.1 306 255.255.255.255 255.255.255.255 On-link 10.58.5.89 276 255.255.255.255 255.255.255.255 On-link 192.168.0.85 276 The binding order for the interfaces is as follows: I've not configured the VPN tunnel to use the default gateway at the remote end, and network comms to nodes on both networks are fine. (i.e. I can ping any node on our network or the remote network). I've modified the PPTP connection properties to use the DNS servers 10.58.3.32 followed by 192.168.0.16, yet the query still goes to 192.168.0.16. Edit: The local resources that disappear are hosted on domain DFS roots, which might (or might not) be relevant.

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• Email not working on testing site in Plesk before DNS switch

  - by Dilip Rajkumar

  I have to test my website before my DNS is swtiched to the new server. My New server is having Plesk. I changed my hosts file to point to the new server and I tested the site. My Site is working fine. However, When I try to register I have 2 emails sent one to the user and one to the admin. Admin email id is same as the server name for example my site name is test.com the admin email is [email protected]. So email is not sent to the admin. I know the email is not sent because the Plesk his searching its own dns instead of Global public DNS. Do any one know how to make my site see public DNS on sending email in Plesk. If I set Goole Public DNS 8.8.8.8 for MS record will it work.. Please guide me. Thanks in advance..

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• What's a nice explanation for recursion?

  - by Gulshan

  This question is inspired by What's a nice explanation for pointers? So, what can be a nice explanation of the recursion? Update: The idea of recursion is not very common in real world. So, it seems a bit confusing to the novice programmers. Though, I guess, they become used to the concept gradually. So, what can be a nice explanation for them to grasp the idea easily? I expected some detailed answers. N.B. : Even I am going to post one answer. But to be fair, it will be few hours later.

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• Recursion VS memory allocation

  - by Vladimir Kishlaly

  Which approach is most popular in real-world examples: recursion or iteration? For example, simple tree preorder traversal with recursion: void preorderTraversal( Node root ){ if( root == null ) return; root.printValue(); preorderTraversal( root.getLeft() ); preorderTraversal( root.getRight() ); } and with iteration (using stack): Push the root node on the stack While the stack is not empty Pop a node Print its value If right child exists, push the node's right child If left child exists, push the node's left child In the first example we have recursive method calls, but in the second - new ancillary data structure. Complexity is similar in both cases - O(n). So, the main question is memory footprint requirement?

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• Performance: recursion vs. iteration in Javascript

  - by mastazi

  I have read recently some articles (e.g. http://dailyjs.com/2012/09/14/functional-programming/) about the functional aspects of Javascript and the relationship between Scheme and Javascript (the latter was influenced by the first, which is a functional language, while the O-O aspects are inherited from Self which is a prototyping-based language). However my question is more specific: I was wondering if there are metrics about the performance of recursion vs. iteration in Javascript. I know that in some languages (where by design iteration performs better) the difference is minimal because the interpreter / compiler converts recursion into iteration, however I guess that probably this is not the case of Javascript since it is, at least partially, a functional language.

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• Resources for improving your comprehension of recursion?

  - by Andrew M

  I know what recursion is (when a patten reoccurs within itself, typically a function that calls itself on one of its lines, after a breakout conditional... right?), and I can understand recursive functions if I study them closely. My problem is, when I see new examples, I'm always initially confused. If I see a loop, or a mapping, zipping, nesting, polymorphic calling, and so on, I know what's going just by looking at it. When I see recursive code, my thought process is usually 'wtf is this?' followed by 'oh it's recursive' followed by 'I guess it must work, if they say it does.' So do you have any tips/plans/resources for building up your skills in this area? Recursion is kind of a wierd concept so I'm thinking the way to tackle it may be equally wierd and inobvious.

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• Server 2008 R2 Dns Lockup

  - by Richard Maynard

  Hi, We've deployed our first 2008 R2 server on a client site which has replaced their existing 2003 DC. This server provides DNS resolution services to all client machines on that site for general internet usage. Since using the 2008 R2 DNS services we have noticed every couple of days the DNS server starts timing out when requests to certain sites are made (google is the only example I can provide at this time although it seems to be larger sites with problems rather than small - CDN compatiblity issue?). When you restart the DNS Server service then resolution returns to normal... just only for a day or so. Is anybody aware of any significant changes to the DNS server architecture or configuration out of the box in R2 that may explain this intermittent behaviour? I have already tried the fix listed here to no avail: http://weblogs.asp.net/owscott/archive/2009/09/15/windows-server-2008-r2-dns-issues.aspx The following PS command prompt info illustrates the issue: PS C:\Users\Administrator.UK> nslookup Default Server: s8209001.uk.kingdomfaith.com Address: 10.1.3.4 > www.google.com Server: s8209001.uk.kingdomfaith.com Address: 10.1.3.4 Non-authoritative answer: Name: www.l.google.com Addresses: 66.102.9.99 66.102.9.104 66.102.9.105 66.102.9.103 66.102.9.147 Aliases: www.google.com > www.google.co.uk Server: s8209001.uk.kingdomfaith.com Address: 10.1.3.4 * s8209001.uk.kingdomfaith.com can't find www.google.co.uk: Server failed Thanks in advance. Regards,

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• Server 2008 R2 DNS Lockup / Stops Resolving Internet Names

  - by Richard Maynard

  We've deployed our first 2008 R2 server on a client site which has replaced their existing 2003 DC. This server provides DNS resolution services to all client machines on that site for general internet usage. Since using the 2008 R2 DNS services we have noticed every couple of days the DNS server starts timing out when requests to certain sites are made (google is the only example I can provide at this time although it seems to be larger sites with problems rather than small - CDN compatiblity issue?). When you restart the DNS Server service then resolution returns to normal... just only for a day or so. Is anybody aware of any significant changes to the DNS server architecture or configuration out of the box in R2 that may explain this intermittent behaviour? I have already tried the fix listed here to no avail: http://weblogs.asp.net/owscott/archive/2009/09/15/windows-server-2008-r2-dns-issues.aspx The following PS command prompt info illustrates the issue: PS C:\Users\Administrator.UK> nslookup Default Server: s8209001.uk.kingdomfaith.com Address: 10.1.3.4 > www.google.com Server: s8209001.uk.kingdomfaith.com Address: 10.1.3.4 Non-authoritative answer: Name: www.l.google.com Addresses: 66.102.9.99 66.102.9.104 66.102.9.105 66.102.9.103 66.102.9.147 Aliases: www.google.com > www.google.co.uk Server: s8209001.uk.kingdomfaith.com Address: 10.1.3.4 * s8209001.uk.kingdomfaith.com can't find www.google.co.uk: Server failed

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• In spite of correct DNS, Exchange sending to wrong destination server for single outbound domain

  - by beporter

  My company uses an SBS 2003 server and makes use of Exchange to host our own email. We also have a linux server hosting domains for some of our clients. In order for us to send to those clients, we had internal DNS set up to shadow the client domains to provide "correct" MX records inside our network. For example, public DNS for a domain abc.com might point to 1.2.3.4, but internally we have MX records set up to route mail for abc.com to 172.16.0.4, which is the linux email server. This setup was entirely functional; this is just back story. We've recently moved one of our client domains from our internal linux server to an external email provider. When we did that, we naturally deleted our internal shadow DNS records so our Exchange server would fetch correct (public) DNS records and route mail out to the new external host. This has NOT had any effect on Exchange though. Even after rebooting the Exchange server and completely flushing the DNS cache (nslookups on the Exchange machine itself correctly resolve to the new external address) Exchange still attempts to deliver messages for the domain to our internal server! Exchange correctly routes to all other internal and external domains when sending email. Somehow Exchange is trying to deliver to a machine that by all accounts it has no business trying to use for just this one domain. Is there a DNS cache that Exchange uses internally? Is there a way to flush that internal cache? What else could I be missing?

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