Strange issue: modem stop releasing dns when pc with sophos is connected

Yep, it's a very strange issue, but I did many experiments and this is what I verified.

I have a "Fastweb" Askey RTV1907VW modem.

Since I installed sophos beta in my pc, after a few minutes I connect my pc to the modem with Wifi, my web browsing stops because dns is no more responding.

All other devices connected to the modem can't browse because of dns problem.

If I restart the modem it works correctly: if I connect the pc with sophos beta after few minutes it hangs again.

I tried to uninstall sophos and it work correctly.

If I reinstall sophos and reconnect it hangs.

If I manually set dns to my pc it works also when modem "hangs"

 

Quite strange, isn't it?

 
  • No ideas on what's happening?

  • Hi Francesco, 

    Could you check the DNS settings and share the same with us. 

    Recommended DNS : 8.8.8.8, 4.2.2.2 4.4.2.2 etc . 

    Check the NSlookup on your system and check if the DNS is resolved or not. If not please check your Modem as it has nothing to do with Sophos Home. 

    As per your experience, I believe that there is some issue with your Modem and unable to resolve the request. You may do a series of test and since you have isolated the issue with DNS, change the DNS settings and validate again. 

  • I highly doubt that Sophos would be changing settings on the modem. 

    1. Is the unit just a cable modem or is it also a wifi router?  If there's a separate router maybe the issue is on that end.

    2. Is the firmware on your modem up to date?

    3. If you are renting the modem from your ISP you should be able to get a free replacement to see if issue is hardware related.

    4. In the modem's config page, are there settings for DNS? Is it set for default ISP DNS servers (automatic) or manually / statically entered.  If it's set to automatically use the ISP's DNS, change it to what the previous post mentioned (Google's DNS servers), or I use OpenDNS servers that I type in manually at the router level so that all the machines connected to my router uses it without changing anything on their computer / devices.

    I see from Fastweb italian website that another user has an issue with DNS and your modem

    https://translate.google.com/translate?hl=en&sl=it&u=http://www.fastweb.it/forum/servizi-rete-fissa-tematiche-tecniche/fastgate-askey-rtv1907vw-e-problema-dns-t18038.html&prev=search

     

    Patrick

  • In reply to Pat B.:

    Hi Patrik, 

     

    1. Is the unit just a cable modem or is it also a wifi router?  If there's a separate router maybe the issue is on that end.

    Ans: You may need to confirm the modem DNS settings, if you are using a PPPOE then the DNS address should be mentioned. You could alter the DHCP settings to set the DNS servers for your clients. So when the DHCP request is initiated, your systems would receive the DNS set as per the DHCP settings.  A better explanation would help if there is a network diagram with IP addresses.

    2. Is the firmware on your modem up to date?

    Ans: That is something you may check on the website of the vendor if they have a later firmware.

    3. If you are renting the modem from your ISP you should be able to get a free replacement to see if the issue is hardware related.

    Ans: Agreed, If you find a fault with the device and rented out by your ISP. Please advise them to fix this issue or for a replacement.

    4. In the modem's config page, are there settings for DNS? Is it set for default ISP DNS servers (automatic) or manually / statically entered.  If it's set to automatically use the ISP's DNS, change it to what the previous post mentioned (Google's DNS servers), or I use OpenDNS servers that I type in manually at the router level so that all the machines connected to my router uses it without changing anything on their computer/devices.

    Ans: you may use Google DNS as you would wish and strongly advised. It may occur that the DNS settings provided by your ISP is not functional.