0

Does anybody know why I cannot connect to the internet when my Server is down?

Problem:
1.) My Windows 7 machines cannot connect to the internet when my Windows 2012 server is down. 2.) My Windows Vista machines cannot connect to the internet when my Windows 2012 server is down.

Note: The browser error that I get is "...DNS address could not be found."
Note: The ping error that I get is "Could not find the host"
Note: LAN connections work

Setup:
► Server OS = Windows Server 2012 Essentials

    Web Server Role (IIS)

    DNS Server Role

► Modem
► Router (DHCP Server)
► Port Forwarding 53 (DNS)

Situation:
The problem presents itself under these conditions:

  1. I turn off the Server
  2. I remove port forwarding 53 (ie, I make my router the DNS Server again)

Summary:
When I attempt to stop forwarding the DNS role to my Server the rest of my computers still fail to access the internet.

Does anybody know why?

Thank you.

  • If the hosts are configure via DHCP to use your server as the DNS server, then it would make sense that your hosts cannot use DNS to resolve names to addresses. That does not mean that your Internet is down. The Internet still works correctly, only the applications which use DNS can't resolve names to addresses. I would bet that you could still contact anything on the Internet. For example, try to ping 8.8.8.8 when your situation happens. – Ron Maupin Oct 1 '16 at 5:00
  • Your first sentence is what I believe I need to look into, but I don't fully understand. – FinPro.Online Oct 1 '16 at 5:39
  • Here are the answers to your questions:►1.) Yes, a ping of "8.8.8.8" works (when my server is down). 1a.) However, a ping of "google.com" does not work (when my server is down). – FinPro.Online Oct 1 '16 at 5:39
  • Technically, you can connect to the internet. You just can't resolve hostnames. If you know the IP address of a website, you could type that into the address bar and access the site. If your 2012 server is going to be down on a regular basis, you should configure public DNS servers on your client machines. – Charles Burge Oct 1 '16 at 9:44
  • @CharlesBurge | Yes. My "client" computers can still connect via direct IP Address calls. So, I guess I could configure public DNS servers on each client machine. It's just that I don't know anything about that, and it doesn't sounds ideal. I feel like I've discovered a symptom to a problem in my network setup. Is Google my best bet for the client machine DNS server configuration? – FinPro.Online Oct 1 '16 at 10:27
3

When your Windows 7 machines start up, they go through a DHCP discovery process to obtain an IP address and (most importantly for you) DNS settings.

DNS is used to resolve domain names (e.g. google.com) to IP addresses. This is essential for browsing the web. Without DNS you'd need to know the IP address of all the sites you intend to visit

When your server is powered off:

  1. DNS is down - so your Windows 7 clients can't resolve domain names to IP addresses (a broken internet experience)
  2. DHCP is down - so your Windows 7 clients can't retrieve new details via ipconfig /release or /renew

So that's why they can't browse the web.

As a quick fix, configure your server's DHCP role to provide Google DNS (8.8.8.8) as secondary. That way when your server is down, your Windows 7 clients will use Google DNS to resolve domain names instead - allowing the internet experience to continue

In the longer term, consider the following:

  • Does your server need to provide DHCP and DNS services at all? Or could you rely on your router for this?
  • If you do want to provide these services on your internal network, consider resilience options:
    • Bringing up multiple DNS servers on your network
    • Enable DHCP failover options
    • Depending on the size of your network, this could be overkill

Hope this helps!

  • @JamesFMackensi | ► 1.) No, I do not think my physical server needs to provide DHCP or DNS services. I've got it doing DNS because that was the only way I could broadcast my website. ► Note: I have a very small network (6-7 computers, 2-3 other devices). – FinPro.Online Oct 1 '16 at 21:20
  • How would you like to make your website available? Internally for your private network or on the public internet? In either case your server shouldn't need to host DNS/DHCP to achieve it. Thanks! – jamesfmackenzie Oct 3 '16 at 6:40
0

It sounds like you need to enable a better failover solution or simply allow the router to handle DNS all the time. I doubt the PC's are going to get the correct DNS settings until you do a release/renew on DHCP or perform a flushdns command. Even though you are removing the port forward, you are not removing the DNS settings in cache for each machine.

  • Thanks, Justin. Yes, I do believe I need to make use of the proper method. My initial goal = Get a Web Server to broadcast my website on the WWW. My initial method = Configure IIS + Activate DNS (IIS was to map ports to internal AppPools, DNS was for broadcasting). Long story short, I gave one Server two roles because that's the only way I could accomplish my goal. I'm not sure I did it the right way (this internet access problem is a reason for my doubts). – FinPro.Online Oct 1 '16 at 5:56
  • Here are the answers to your questions. 1.) No, unfortunately, running ipconfig /release did not solve the internet problem. 2.) No, unfortunately, running ipconfig /renew did not solve the internet problem. 3.) No, unfortunately, running ipconfig /flushdns did not solve the internet problem. 4.) No, unfortunately, none of these command combinations solved the internet problem. ►► Note: I ran all of these commands on my "client" computers. ◄◄ – FinPro.Online Oct 1 '16 at 5:59
  • When you changed the DNS back to the router, did you actually enable the DNS service or just remove the port forward? Does a router reboot fix it after the change? – JustinV Oct 1 '16 at 6:01
  • Here is another thought. On your server, configure a secondary DNS server. Use 8.8.8.8 or 75.75.76.76. If the server goes offline, the primary DNS will fail and should kick over to the secondary DNS. – JustinV Oct 1 '16 at 6:03
  • You can also have more than one DNS server on your local network. So you can enable DNS by default on your router and server. Remove the port forward. Add both DNS to your DHCP server settings. Make the router secondary. If the server goes offline, internet should stay by using the routers DNS. – JustinV Oct 1 '16 at 6:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.