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Pastimes : Computer Learning -- Ignore unavailable to you. Want to Upgrade?

To: Gottfried who wrote (49289)	1/27/2006 12:29:45 PM
From: LTBH	Respond to of 110655

windowsnetworking.com Checking Name Resolution 101 This article is laid out so that it will show you how to not only use the tools, but also how to pick them. This is helpful because to just learn the tool’s name and all the switches you can use with it may not be particularly helpful to you if you don’t know when you would use a particular switch with a command. I have seen this a million times in books that are trying to drill this information into your head so that you remember it, problem is, if there is no scenario, you know, a real world – in the pits – scenario, pure memorization of the tool and its switches becomes pointless then because although you may have them memorized, how would you use them to resolve problems? Consider Ping. Why would you use a Ping command with a ( -a ) switch? Let’s consider a problem where you would have to test DNS resolution, a user can’t get to an Internet website. Now, I know there are many ways you can test to establish what the problem is but let’s assume we wanted to quickly see if DNS was the problem, we isolated the problem that far, it’s definitely something wrong with DNS resolution. The DNS Cache was also flushed (ipconfig /flushdns which purges the DNS Resolver cache). So now, we will quickly test DNS with Ping? Yes, Ping with a particular switch can be used to solve a problem such as ‘why can’t we get to that URL, http://compIntranet?’ Well, do you know if you have DNS resolution such as a HOST file entry or the company DNS server assignments in the TCP/IP configuration properties configured via a DHCP server? Test DNS on your local PC to make sure you aren’t the problem first. If you get a complaint that users can’t get to http://compIntranet then you should make sure that you aren’t the problem first. Make sure you have DNS resolution. You can do this many ways, but one of the ways you can do it with the Ping command is with the ping –a ip_address command which will try to query resolve DNS to find out what the host name is. 1. You have to see if DNS resolution is working you can see if the DNS server you are configured to query knows what it’s talking about. Using the NSLOOKUP command shows this information. C:\WINDOWS\SYSTEM32>nslookup Default Server: ns3.srv.hcvlny.cv.net Address: 167.206.112.3 > www.yahoo.com Server: ns3.srv.hcvlny.cv.net Address: 167.206.112.3 Non-authoritative answer: Name: www.yahoo.akadns.net Addresses: 216.109.118.74, 216.109.118.75, 216.109.118.77, 216.109.117.110 216.109.117.204, 216.109.117.205, 216.109.118.69, 216.109.118.71 Aliases: www.yahoo.com 2. When I query my local DNS server, I can see that Yahoo.com has multiple IP addresses that can be used. 3. Now, it’s possible to ping with the –a switch to also verify if DNS resolution is work. Pinging Yahoo’s IP address with the –a switch produces the DNS name of the system. C:\WINDOWS\SYSTEM32>ping -a 216.109.118.74 Pinging p11.www.dcn.yahoo.com [216.109.118.74] with 32 bytes of data: Reply from 216.109.118.74: bytes=32 time=22ms TTL=51 Reply from 216.109.118.74: bytes=32 time=25ms TTL=51 Reply from 216.109.118.74: bytes=32 time=27ms TTL=51 Reply from 216.109.118.74: bytes=32 time=32ms TTL=51 Ping statistics for 216.109.118.74: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 22ms, Maximum = 32ms, Average = 26ms Although a simple example of using command line tools, we were able to also see why we would want to use them. See, so this guide does just sound like a machine telling you that ping is a command line tool that uses the ICMP echo protocol to send packets to … blah, blah, and blah! It’s a useful guide to help you understand why you would use them as well. It also shows you why you would use such switches that are available with the most common tools! Hopefully this will help you know when to use each one and help you create that precision needed in your troubleshooting steps. We will be back next time with some command line tool tips.

To: Gottfried who wrote (49289)	1/27/2006 12:55:39 PM
From: LTBH	Read Replies (1) \| Respond to of 110655

And here's some more (symptom/problem slightly different but solution same): handcoding.com April 15th, 2005 Alternate DNS Servers The other day, my Internet connection went down — well, I didn’t see it go down but, when I got back from work that day, I couldn't browse anywhere. And, what would often help in the past would be to reboot my cable modem; so, I tried that about three or four times (and, really, I should have caught on after the second time). Comcast hasn’t been incredibly reliable for me — they tend to go down every couple months — and I just chalked this up to their usual ineptness. I then noticed a curiosity — my IM client was still online. And I could still read my mail. But I couldn't browse the web (whaa?). I wondered for a moment whether Firefox was acting up and so I tried loading an ftp client to test my connection. (You thought I might load IE for that? Not if I can help it ;).) Sure enough, FileZilla couldn't connect anywhere either. Then it hit me: my DNS had probably gone wonky. That would explain why I couldn't browse anywhere but my most common Internet apps still held up — those ip addresses were cached by my OS. At that point, I ran “ipconfig /all” and then pinged the DNS servers to which I was assigned. To no surprise, they both timed out. Then, on a hunch, I tried loading Google and I was actually able to make it there (since I suppose its ip address was one of those in my cache). I then tried searching for “alternate DNS servers”. There were quite a few hits but, of course, I couldn’t see any of them since those sites weren’t in my existing DNS cache (d’oh!). It then dawned on me that I could view the Google Cache of those pages; and, while the pages probably wouldn't look pretty, that would hopefully allow me to get the info I needed. Indeed, Google Cache worked nicely and I found some alternate DNS servers that I could use. I popped those in my settings and I was up and running again. However, I realize now that I could have made things easier on myself by keeping a few spare DNS servers on hand — before they actually went down. In any case, while there are dozens of DNS servers which are suitable, some that were mentioned consistently were the 4.2.2.x series (4.2.2.1 through 4.2.2.6). I did an nslookup on those ip addresses and they came back as Genuity.net and GTEI.net servers. Perhaps ironically, I can’t load either of those domains right now, otherwise I’d include a sentence about who each of those companies are ;). But, with such low-numbered ip addresses, I presume they’re of some importance within the InterWeb. In any case, one of the comments on Digg.com [] offers these instructions for adding DNS servers in case you haven’t done that kind of thing before: Click on “My Computer”. Click on “My Network Places”. Click on “View Connections”. Right click on the connection that supports your Internet connection and go to “Properties”. Double click on the Internet Protocol TCP/IP option. Make sure “Use the following DNS server address” is selected, and input the above recommended DNS. To check go to “Start > Run > “cmd” ”. Type in “ipconfig /all” and you should see the DNS you input where it says “DNS”. [] On a side note, what is Digg, anyway? Pages within digg.com have been coming up in my search results more frequently recently but I can't quite wrap my head around what the site is about. Something about folksonomies, I’m guessing. Anyway, before adding those DNS servers, you may as well ping each of them to see which of them are fastest for you. If you go through all six of them, just pick (say) the two with the lowest ping times. Granted, it’s all a matter of milliseconds but every little bit helps ;). posted by Alex at 10:12 pm in dns, comcast, broadband LTBH NOTE: One common misconception is to think that the purpose of the list of proxy DNS servers configured in one's DNS Client is to provide fallback in the event of the receipt of a negative answer, thinking that if a "no such name" answer is received by the DNS Client from one proxy DNS server it will consequently fall back to querying the next. This misconception is false. The fallback mechanism is not there for the provision of some hypothetical mechanism for somehow admixing multiple different proxy DNS services. If a DNS Client receives a response containing a negative answer, it will use that answer. As far as it is concerned, it has an answer. It will not continue to look for another one, and it will not attempt to mix in the service of a different proxy DNS service. Fallback occurs in the event of a lack of response, within the DNS Client's timeout period, not in the event that a response is actually received.

To: Gottfried who wrote (49289)	1/27/2006 1:25:57 PM
From: LTBH	Respond to of 110655

Gottfried Normally I would not have expended this much time for something I believe you could also research, HOWEVER it pxssxd me off that I could not remember the program's name I had used couple years ago which also provides the how/where for alternate addresses. At least I was correct in that its Canuck. Finally found it: called Treewalk, recommend you read their stuff and if decide to try (its free) would virus scan pre installation .... Have NO reason to believe there will be any issues ... just normal prudence and caution. FWIW and now I go back to watchin my stocks: ntcanuck.com More About TWDNS From: What does TreeWalk do? Essentially, putting a "name" into the browser doesn't get you anywhere. The "name" must be translated into machine recognizable numbers (octets) such as 216.239.37.99 which takes you to Google.com (the Google Search Engine). Briefly, let's look at the current make-up of today's Internet and TreeWalk's interaction within that scenario. We'll also mention a few of the tools that come with TreeWalk, which are available from the program group (click the "Start" button, select "All Programs" or "Program Files" and navigate to the "TreeWalk" folder to select either the "config" or "tools" icons for more menu choices). Most ISPs use the ICANN root name servers and if there is a problem with those servers, that problem reflects right back to your ISP's DNS servers. Perhaps you will get spotty, irregular DNS service and sometimes your ISP's DNS will fail you completely. "TreeWalk DNS" was written by ObiWan and NT Canuck to provide an alternative to total reliance on your ISP's service, by providing localized hostname resolution for common Operating Systems that normally do not have this capability. TreeWalk caches DNS results locally, which are stored in RAM before being written to disk so such data is still available after a reboot of your computer. TW checks for a local record of any browser, email, Instant Messenger, FTP, Newsgroup (etc.) request that you initiate. If it doesn't find one, it "goes out and gets one", stores that record to RAM and subsequently writes it to a file for future referencing. TreeWalk can do this through your Internet connection even if your ISP's DNS servers are struggling for any reason. The TW install routine moves the Primary DNS server for your ISP into the Alternate DNS server position in your Networking Properties so that if a configuration or other local error interrupts the TW Service, your machine will look to the secondary server in the list (which was formerly your Primary DNS server), and will resolve names through that route instead. Upon uninstalling TW, all your previous settings are restored exactly. If TW was installed properly, you usually shouldn't ever need to uninstall it. If you read and adhere to the information presented by the installer you'll be up and running your own Personal DNS Server quickly and easily, after a simple reboot of your computer! In the unlikely event that the local TreeWalk server and your ISP's servers all fail to resolve names at the same time, you can still try updating the ICANN root-hints anyway (as a further test) or you can try the ORSN root-hints. If all of the above fails, a call to your ISP might be in order to verify that you currently have Internet Service in your area. If you use a Root plug-in for TreeWalk, this changes the scenario somewhat. Caching and other features are still enforced but plug-ins use a specific root zone file based on your choice of plug-in. Using a plug-in usually assumes and suggests some type of low-level monitoring, such as in a LAN environment. Generally you will not need to update any root-hint files, but the authors have provided this capability (and others too) for users who might have a more complicated configuration, like a local LAN server for example. The tools included with TW are more for troubleshooting than anything else and should be left unused by the more basic users as they are not intended as toys to play with. The "Backup" and "Restore Backup" tools should definitely be used to save any working TreeWalk configuration before performing any tests, so that the configuration can be re-instated in case of any unintentional or accidental user error. This is similar to what you might see if you have a default install of TW and update the ORSC root-hints: Getting file zone.orsc from DNS server 199.166.24.1 Stopping the DNS service daemon The twdns service is stopping. The twdns service was stopped successfully. Replacing file named.root with zone.orsc 1 file(s) copied. Deleting file zone.orsc Zapping the cache file Starting the DNS service daemon The twdns service is starting. The twdns service was started successfully. All done, check for errors and then Press any key to continue . . . What's happening is TW is downloading a zone file and updating the named.root file with it's content, by executing a batch file. This is what you might see if you have a default install of TW and update the ICANN root-hints: Getting file zone.icann from DNS server 198.41.0.4 Stopping the DNS service daemon The twdns service is stopping. The twdns service was stopped successfully. Replacing file named.root with zone.icann 1 file(s) copied. Deleting file zone.icann Zapping the cache file Starting the DNS service daemon The twdns service is starting. The twdns service was started successfully. All done, check for errors and then Press any key to continue . . . ...and similar for ORSN. If you're using a slave-root plug-in you'll see procedures similar to the above, but keep in mind that the plug-ins use their own root database files so whatever servers are listed in named.root will be used for lookups after an uninstall of the plug-in. Only one Root plug-in can be installed at any one time and any existing plug-in needs to be uninstalled before trying another. These add-ons install and uninstall very quickly, with no reboots required. In either case, you can use TreeWalk rather than simply using and relying on your ISP's servers but the root-slave plug-ins will auto-update themselves at regular intervals. The "Update root-hints from [root]" tools are ineffective and not required when using our plug-ins. If you employ the default install of TW you still have the option of choosing your preferred root zone, but keep in mind that this should be done only as required, for many good reasons. Forums for TWDNS Support: TreeWalk Support forums and newsgroups provide TreeWalk users with access to shared help and advice. If you're going to post a message asking for help with your TreeWalk problem, please be sure to include specific details about your computer (memory and processor speed), Operating System, connection type (how you connect to the Internet), third party software (anti-virus, anti-Trojan, firewall, anti-scripting, etc.), the version of TreeWalk (or BIND-LE) you're using, networking configuration and hardware, and any relevant error messages. This will aid greatly to find the solution for your problem as soon as possible. The forums and newsgroups contain exactly the same postings but offer a choice of access method via browser, news reader or RSS/Atom. Currently there are no requirements to register at the site as a user. However a number of features are being introduced such as "Own Article Delete" that will require replying to a registration URL sent via email. "Free if used for educational or home use" users of TreeWalk are invited to join in discussions taking place in the forums and place support questions in the forum ntc.support.questions. Licensed users should continue to contact the TreeWalk site for private email support but are still invited to take part in general discussions. So Luck in your Efforts LTBH