DNS errors

[techb]

I have had several customers at work with supposed DNS issues.


This is all DSL is it makes a difference, but the story is as goes.
Modem shows everything is okay, line tests are okay as well, they get a WAN IP and can authenticate whether it be PPPoE or a Routed Bridge/DHCP connect with the ISP, they get a routable IP from us.


All browsers including IE, Firefox, Chrome don't work. Windows diagnostics say it is a DNS issue. TCP/IP settings are good and they get a good working private/LAN IP. With DNS adress selected as obtain automatic and with googles 8.8.8.8/other including Nortians DNS addresses don't work. They have a hardwire connection to the modem/router combo we provide. All physical looks good, no splitters or filters on the line. Device Manager is okayed with correct and updated drivers. WinSock reset doesn't give any results either.


I had a customer try a different modem/router they had on hand, same model and everything and it worked.


My conclusion is it is a defective modem/router. But, it has happened with multiple modem/router models we have and with three different occasions this has happened with three diff models.


I know there was a recent DNS virus to hit the public, but on all the systems no Antivirus has picked it up including Nortian, McAffee, F-Secure, MalwareBytes, EasyClean, CCcleaner, Windows Security (the one windows offers now apparently) can find anything wrong including in the registerys. Windows has always been up-to-date, I can't really verify the OS version though.


Just wondering if any of you have had the same problem, or something I am missing. From what I understand why would the modem/router be the issue? I thought DNS didn't really have anything to do with the modem/router.


Any insight?

[silenthunder]

How about the possibility of bad firmware/software on either the modems or routers? I had somehow gotten a corrupted update on my router and it stopped working, but everything else checked out OK as you mentioned. I'm not the network administrator at home, but my mom did one of the first steps in troubleshooting: redo the last update/reinstall the latest firmware/software and it worked just fine. Also on DSL btw.

[techb]

How about the possibility of bad firmware/software on either the modems or routers? I had somehow gotten a corrupted update on my router and it stopped working, but everything else checked out OK as you mentioned. I'm not the network administrator at home, but my mom did one of the first steps in troubleshooting: redo the last update/reinstall the latest firmware/software and it worked just fine. Also on DSL btw.

Update on the firmware of the modem/router or computer?

[silenthunder]

The modem/router. I'm not sure which one she updated though, but considering she just replaced the router I'm assuming that's the one. We've had our modem for about a year, but our router had to be a good 3-4 years old.

[techb]

When I say modem/router we have a modem router combo meaning a router is built into the modem we provide. I know it has to be router specific issue, but even then I don't see where anything DNS should be in the router itself. Unless I am mistaken, the DNS should be PC specific or something cloud related.


Then again, I'm no expert, just wondering if anyone else has seen these issues and what has been done to fix it. I will continue replacing modem/routers in the mean time until I get more feedback or pointed to something else besides firmware issues.


I thank you for your feedback though silenthunder.

[iTpHo3NiX]

Hrm sounds to me like its a router/modem issue. I've never had good luck with modem/router combos always seem to be faulty.

Have you tried manually setting DNS servers? As well as flushing the DNS (assuming windows based systems)

Code: [Select]

ipconfig /release
ipconfig /flushdns
ipconfig /renew

[techb]

Hrm sounds to me like its a router/modem issue. I've never had good luck with modem/router combos always seem to be faulty.

Have you tried manually setting DNS servers? As well as flushing the DNS (assuming windows based systems)

Code: [Select]

ipconfig /release
ipconfig /flushdns
ipconfig /renew

Yeah, I did flush the dns, and resolved the cache successfully. Did renew the ip though since it was already getting a valid one along with a default gateway. Even hard  reset the modem/router.

I  guess they must have pushed an update to the firmware that borked the system or something.

[geXXos]

What if you reboot the DNS server.

[Dijkstra]

I wonder if you would have been able to ping 8.8.8.8? That would tell you if it was just a DNS issue or a bigger issue. Of course if replacing the modem solved the issue it then that just leaves more questions! Is it a SOHO router? Or was it a router/modem that the ISP provides?