Users who try to flush the dns cache might receive the error message “Windows IP Configuration Could not flush the DNS Resolver Cache: Function failed during execution” if the DNS Client service is deactivated.

The solution to fix this error message is to enable the DNS Client service again in the Services configuration menu. I’m not sure if it makes that much sense to flush the cache if the DNS Client is disabled as it should mean that Windows is not resolving and storing DNS at all. Experts who might to weight in are encouraged to do so.

You can start the service by typing [Windows R], [services.msc] [enter]. Locate the DNS Client service, right-click it and select properties from the menu.

You need to set the service to manual or automatic before you are able to start the service.

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Naturally if you have such a server, you have to have the ability to configure that server. One of the configurations you most likely will need to undertake is the configuring of network settings for a static IP address on your headless, GUI-less server. Fortunately, when using Ubuntu Server 8.10 – that is a piece of cake.

In reality there are two files that must be configured and one file that can be configured. The “must files” are /etc/network/interfaces and /etc/resolv.conf. The “can file” is /etc/hosts. We will deal with the former two files in this article. The latter file (a file that deals with local IP to name mapping) has already been covered in my article “Ease Linux Networking with /etc/hosts” here on gHacks.

So let’s first take a look at the most important file, /etc/network/interfaces. Open that file up in your favorite editor (mine being nano).? What you will most likely see is this:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
auto eth0
iface eth0 inet dhcp

The last line is what you need to edit (and add to.) To configure eth0 (your network device) for a static IP address that last line should resemble:

iface eth0 inet static
address 192.168.1.10
netmask 255.255.255.0
gateway 192.168.1.1

Naturally you will need to change the last three lines to reflect your own networking setup.

Once that file has been edited you can restart your network connection with the command:

sudo /etc/init.d/networking restart

Your Ubuntu Server 8.10 should now be up and running with a static IP address.

DNS

There is one last file you will need to take care of. That file is /etc/resolv.conf. This file is in charge of holding your DNS server addresses. Open this file up in your editor. What you need are two lines:

nameserver 208.67.220.220

nameserver 208.67.222.222

The above example reflects using the OpenDNS servers. Your network will obviously have its own requirements for DNS addresses. Once you have edited that file save it and you’re done (no need to restart networking for the change in DNS addresses to take effect.)

Final Thoughts

That’s it. How simple is it to configure your Ubuntu Server with a static IP address – even when said server is a headless, GUI-less server. Of course there is much more you can do than simple Static IP address configuration, but this just highlights how easy a Linux server can actually be to administer.

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They did provide a switch in the user control panel to disable that feature again but this is again a company that is forcing the user to take action for something that they changed.

Open DNS has been covered before on this website and I just want to remind everyone that Open DNS can be used to get rid of search boxes from your provider. Setup of Open DNS takes a few minutes at most and should be doable for everyone.

By using the service you start using the Open DNS servers instead of the ones from the Internet Provider. DNS meaning Domain Name System which is responsible for “translating” domain names into IP addresses.

Open DNS provides additional advantages such as phishing protection (that is not slowing down your computer), parental controls, typo corrections and shortcuts. Shortcuts work like Firefox keywords, you basically assign a phrase to an url and can use the phrase to open the website.

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Those lookups are handled by dns servers and recently a serious vulnerability has been discovered that makde it possible to manipulate those queries. This could be used to send users to a different location which could open the door for serious phishing incidents. Just think about the possibility to fake eBay or Amazon and send visitors to those fake sites even if they type in the real address.

Doxpara Research, run by security researcher Dan Kaminsky, created a script that is checking if the DNS server that you are currently using is vulnerable to the attack. This is done by pressing a button on their website. I tested the script in Firefox and Internet Explorer and both lookups work fine.

One solution if the DNS server is found to be vulnerable would be to switch to the Open DNS system. David Bradley, an active reader of my website, covered the topic as well on his Significant Figures website.

Is your DNS server still vulnerable? Let me know!

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Free IP Switcher [via Tech Malaya] is the perfect tool for this situation. It offers a one click change of the network settings that require no reboot. Probably the fastest solution if you connect to different networks regularly.

What I really like is the feature to import the current network settings which spares you from the hassle to add them to the IP Changer as well. Different IP settings are available in tabs in the program and it only takes two clicks to activate another configuration.

The program offers several additional settings that can be added if needed besides the obvious ones like IP, DNS and Proxy. The Computer Name and the Workgroup can be changed as well as the default printer of the system. Last but not least it is possible to set the DNS Domain and a Wins Server.

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Checking if a website is up or not should be speedy, you do not want to waste your time analyzing large log files if there is another faster way to accomplish the check. This article is therefor concentrating on methods that reveal results in a matter of seconds which are easy to interpretate.

If you know of a method that is missing let me know and I will check it out and add it if it makes a good fit. On we go with ways to check if a website is really down.

1. Ping

A ping basically sends an Hello to a server waiting for an response. If the response takes to long a timeout will occur. Ping is measured in ms, if it is incredibly high something is wrong with either your computer, the route in between or the destination.

The command is similar in Windows and Linux, just enter ping destination, with destination being an IP or domain name, and wait for the response.

One of the many online scripts that ping servers is located at Ping.eu. It offers other network tools like Traceroute and a port check as well.

2. Traceroute

You can compare Tracerouter with a list of all the roads that you travel until you reach your destination. Only that the roads are the servers in this case that your data is send through to reach their destination. If everything is fine the destination server should appear at the end, if it is not you could get timeouts for instance.

Traceroute Tool from the University of Princeton displays the traceroute between the University and another server on the Internet, you can enter the IP or domain name of the server.

Tracert is the command that you can use in Windows to trace the route between your computer and the destination. Use the command “tracert IP” or “tracert domain” to achieve this. Traceroute is the equivalent in Linux.

3. Domain Name System (DNS)

DNS errors most of the time occur when a website is freshly registered or moving to another server. It usually takes some time to update the DNS records to point at the new server. DNS is providing information much like your phone book is. Domain names are for us puny humans who have troubles remembering those server IP addresses (64.233.161.18 for Google for instance). Problems occur when the Nameservers who translate the human entered domain names into IP addresses have still the old IP in their records while the website is already up and running on the new IP.

You can use the online script DNS Report to receive a detailed report. Green results are fine, red ones point to failures and yellow ones are warnings.

4. Proxies

Proxys can be used to establish connections to websites even if the direct route from your computer to theirs is somehow blocked. You can compare that to visiting a friend and using his computer to connect to a server that you cannot connect to. If it works it is somehow related to your computer or connection.

You can find hundreds of web based proxies at Proxy.org. Try some and see if you can connect to the website.

5. Ask someone

If you have direct contact to other users, be it in IRC, Skype, Instant Messengers or even forums, you can ask them if they would be kind enough to check a particular website for you. That`s practically a substitute to using a proxy.

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Whenever you try to access a website you type its url into the address bar. The url is then send to the DNS server who looks up the IP for that website and sends it back to your browser to be able to make the connection to the website. To censor one would simply return no IP or a different IP that redirects to another website. (something like, no no, this is no website that you should visit, bla bla)

This means that the website that you want to access exists of course but the information on the dns server was changed to prevent access. There are two options that let you access the website. The first would be to simply enter the IP address of the website that you want to visit instead of the url. You can use scripts that are freely available on the internet to lookup the IP of an url.

This method is only working if there is only one url that is using that IP. You are out of luck if many websites are hosted on the same server. The second method which is reliable and working for all occasions helps us in this case.

If you change the DNS server that your computer is using to lookup the IP you will receive the correct result. Let us say that you life in China and that China banned access to Wikipedia. Instead of using a Chinese DNS server you use one from the United States which has the information that you need to access Wikipedia.

OpenDNS, a free service, would be one alternative as would be the following list which I have taken from freerk.com

• dns2.de.net – 194.246.96.49 (Frankfurt, Germany)
• ns1.de.eu.orsn.net – 217.146.139.5 (Hildesheim, Germany)
• resolver.netteam.de – 193.155.207.61 (Alfter-Impekoven, Germany)
• sunic.sunet.se – 192.36.125.2 (Stockholm, Sweden)
• master.ns.dns.be – 193.109.126.140 (Leuven, Belgium)
• ns1.lu.eu.orsn.net – 195.206.104.98 (Belvaux, Luxembourg)
• merapi.switch.ch – 130.59.211.10 (Zurich, Switzerland)
• prades.cesca.es – 192.94.163.152 (Barcelona, Spain)
• michael.vatican.va – 212.77.0.2 (Vatican City, Italy)
• dns.inria.fr – 193.51.208.13 (Nice, France)
• ns0.ja.net – 128.86.1.20 (London, UK)
• nic.aix.gr – 195.130.89.210 (Athens, Greece)
• ns.ati.tn – 193.95.66.10 (Tunis, Tunisia)
• ns1.relcom.ru – 193.125.152.3 (Moscow, Russia)
• trantor.umd.edu – 128.8.10.14 (College Park, MD, USA)
• ns1.berkeley.edu – 128.32.136.9 (Berkeley, CA, USA)
• merle.cira.ca – 64.26.149.98 (Ottawa, Canada)
• ns2.dns.br – 200.19.119.99 (Sao Paulo, Brasil)
• ns2.gisc.cl – 200.10.237.14 (Santiago, Chile)
• ns.uvg.edu.gt – 168.234.68.2 (Guatemala, Guatemala)
• ns1.retina.ar – 200.10.202.3 (Buenos Aires, Argentina)
• ns.unam.mx – 132.248.253.1 (Mexico City, Mexico)
• ns.wide.ad.jp – 203.178.136.63 (Osaka, Japan)
• ns.twnic.net – 192.83.166.11 (Taipei, Taiwan)
• ns3.dns.net.nz – 203.97.8.250 (Wellington, New Zealand)
• box2.aunic.net – 203.202.150.20 (Melbourne, Australia)

Changing the DNS Server is a matter of minutes. It depends on the operating system that you are using. In Windows XP you open the control panel and click on network connections. You right-click your connection and select Properties from the context menu.

Select the Internet Protocol (TCP / IP) and click on Properties in that menu. Click on use the following DNS server addresses and enter a preferred and alternate DNS server into the fields. Make sure you enter the IPs. Apply and close the menu and restart your computer. Once that is done you are using the new DNS server which should bypass the censorship.

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It describes methods to censor websites like blocking url’s via the DNS server that for instance the German government likes to use which can be easily countered by using the IP or an DNS server that does not block the website. So, for every action (censorship) you find the corresponding reaction (bypass). Excellent read for everyone whose country, company or institution has decided to block certain information.

Kinds of censorship described:

• Blocked URL’s via the DNS-server
• Forced proxy server / transparent proxy
• Keyword filter
• Blocked ports
• Software on the client (child protection e.t.c)
• Censorware on the server (inside of networks)
• Whitelist
• IP blocking on the routers

Ways to bypass Censorship:

• Using a different ISP
• Using a not censoring DNS-server
• Using a non censoring proxy server
• Using a Web-2-phone service
• Using a webproxy
• Get Webpages via eMail
• Using steganography
• Using a special proxy like peer-2-peer program
• Special Services

Everything is explained in detail and links are provided where necessary. I have decided to pick out some of the more common methods to censor and bypass information in the coming days – stay tuned.

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This was partially answered in the comments by John Roberts (according to the Open DNS website the VP of Product Development) who confirmed that the connection itself naturally takes longer (in milliseconds) but that the open dns servers were optimized to make up for it. This would of course only be an advantage if the servers of the ISP would not be that optimized. The open dns team soon opens a new server location in London which should speed up things for European users. (not saying that they are slow at the moment, they will just be some milliseconds faster with the server in London). You see what I mean if you traceroute a server in the United States and Europe.

But it is not speed that I would like to talk about. Speed is important but not everything. Open Dns offers two features that your normal ISP does not offer. First, it has a automatic phishing detection routine which warns if you attempt to visit a website that was marked as a phishing website. They do rely on more than one source for up to date information, a nice feature.

Second they do fix typos. Try to access a website like www.ghacks.net and you will automatically be redirected to the correct site. If the typo does not have one solution but more than one a list of possible results will be shown. Nice as well.

They also offer another feature that they are not writing about on their website, maybe because they are unaware of it. Listen up, hehe. Some countries decided to ban domains by banning the dns entries of those domains. If you use the dns of a provider in that country you will not be able to visit that website unless you use the IP address instead.

Another dns server fixes that problem. You are free and ready to visit the website and it will show itself completely. Free Speech at its finest. You might want to try their service if you are living in a country that uses this (weak) method to censor content on the web.

The open dns team published a great guide on how to setup the new dns server on your system and / or router. It normally is only a matter of seconds to enter new dns servers. After that is done you are already using the open dns servers.

If you run into troubles you should try the faq section of their site which has answers to common difficulties.

Oh, I would prefer answers from Allison Rhodes instead of John Roberts if the open dns team wants to comment on this. She just looks that much cuter than him :P (see for yourself)

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