Windows – Clients unable to access certain websites, pages half loading, intermittent internet

domain-name-systemrouterwindowswindows-server-2012-r2

All the PC's on my network are having trouble accessing a certain website (https://frontapp.com/) we need. The main page of the site will load partially, but the text and page will look strange. The 'sign in' page will not load at all, just give a connection error. The issue is not with the site because it loads on my home and mobile internet fine. I believe it is some sort of DNS issue because the VM that has the DNS server can access the internet and the site just fine.

Our network structure:

  • We have a Netgear DEVG2020 as our ADSL modem and a Asus N66U as a wireless
    AP.
  • A server with 2x VM's running Server 2012R2.
  • One VM handles our accounting program and print server
  • The other is running Active Directory, DHCP and DNS. The AD server's internet is fine and will load the site in question with no problems.
  • 4 PC's running Windows 7 (x86). One of these pc's is able to intermittently connect to the website, seemingly randomly. None of these pc's are connected to the active directory/domain. There are no differences in configuration in these pcs.

When the PC's are connected directly via ethernet cable to the router, they are able to connect to Front and their internet is fine.

This issue has only appeared a few days ago. Tech support from the internet company said it was on our end.
Replacing the router/modem doesnt appear to be a possibility: our phones are VOIP and I believe that the phones are tied into the modem so we cant use our own hardware. Also we are in an isolated area, getting a tech support or a new modem would be difficult.

I've tried:

  • Uninstalling and reinstalling the DNS role, deleting DNS cache.
  • Flushing DNS on all pc's
  • netsh int ip reset c:\resetlog.txt and netsh winsock reset
  • Setting the DHCP to have the devg2020 as the only dns server on the network and giving everyone new IP's.
  • Restarting everything
  • connecting the devg2020 directly to a PC. This works fine, leading me to believe it has something to do with DNS.
  • Ping and tracert to frontapp. Get nothing, tracert doesnt even show the router.
  • nslookup on the pcs that cant access it. they get the same result as the DNS server.
  • Took a look at the traffic on one of the pcs with wireshark. Honestly not sure what I'm looking for.

I'd really appreciate any help.

edit: interestingly this morning it worked on some computers this morning. By afternoon, only 2 pc's were able to access it. I cant work it out.

Best Answer

I think I figured it out. I had the router that was used as a Access Point for the wifi put in as a Router in the DHCP server and I believe clients were trying to connect to the internet through it.

I removed it as a router in the DHCP server and everything works now, so fingers crossed.

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