DNS errors

CathJ

CathJ

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I hope someone can help me with this, because I'm getting to the pulling-my-hair-out-and-crying stage.


The setup:
I have a Netgear WiFi router, which connects to the net using my Axxess account. I can connect my phone to my router via wifi, and use the net; or can I connect my laptop to the router via wifi, or via cable.

The problem:
For the past few days, I can't connect to the net via my laptop. I figure it's not the router or the ISP, since I can connect via my phone (and router lights all look correct).

I thought it might be my laptop's wifi card, so I connected it to the router via the cable - still no go. The odd thing is that sometimes I'll be able to ping one or two site only; so mostly I won't be able to ping anything; sometimes I'll be able to ping www.google.com, but not www.gmail.com or www.iol.co.za - but other times I'll be able to ping www.iol.co.za but not www.google.com (when I say "can't ping", I mean it says it can't find the server, i.e. it doesn't get the IP address for the site).

All the sites I can't ping on my laptop, I can browse on my phone.

So it seems that the problem is the laptop, but what are the odds that the wifi card (a PCI card), and the built-in lan card break at the same time? Nothing's changed configuration-wise.

Edit: Forgot to mention something significant: using the cable, I can't access my router's configuration page either (assuming I've got the IP address correct: 192.168.0.1 is fairly standard for the Netgear). And I've tried two different network cables, and neither worked.

I plan to check my laptop against my parents' router this evening, but whether that works or not, I don't really see what to do after that.
 
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ipconfig /all

ping dns servers

switch the servers to alternative dns servers if thats the problemo
 
Phone may be receiving a different dns server or handling caching better
 
Still no go.

Tried it now on my parents' router (different ISP & exchange); same problems. I can ping www.google.com, then can't ping anything else, then lose www.google.com as well.

I tried pinging the dns server given in the other thread, as well as the opendns servers; I get responses back on the ping, but if I set my DNS server to use any of those I still can't ping anything else.

I'm out of ideas... a week or two ago, this all worked perfectly and nothing's changed on my side :(
 
Turns out it was ZoneAlarm that suddenly, and with no indication, decided to block everything (even though it looked like everything was still going through fine).

Did a clean install, and everything seems to be good now.
 
CathJ said:
Turns out it was ZoneAlarm that suddenly, and with no indication, decided to block everything (even though it looked like everything was still going through fine).

Did a clean install, and everything seems to be good now.
Click to expand...

I had a similar problem before, when I changed to OpenDNS servers, suddenly my ZA firewall blocked websites without warning. I just added those DNS servers' IP addresses to Firewall > Zones as Trusted and that solved the problem.

Microsoft issued a major patch in July to fix a DNS security problem but unfortunately that patch screwed up ZoneAlarm (see article) which meant you had to manually add DNS servers as Trusted (as I did above) to solve the problem. ZoneAlarm did release an immediate upgrade that solved the Microsoft problem (ZA version 7.0.483.000). You installed your ZA again... I'm taking a wild guess you downloaded ZA again to install it? Because chances are you installed a newer version that had the July DNS fix in it.

Also, although this is not necessarily relevant to the problem you had, if you can't access the router's configuration IP address in the browser, always check if you have cache/proxy server settings enabled in the browser. Because if you do, then the router's IP address must be added as an Exception in those browser settings otherwise the browser will think it's an external IP address, when it's indeed an internal one on your LAN.
 
Globetrotter said:
Microsoft issued a major patch in July to fix a DNS security problem but unfortunately that patch screwed up ZoneAlarm (see article) which meant you had to manually add DNS servers as Trusted (as I did above) to solve the problem. ZoneAlarm did release an immediate upgrade that solved the Microsoft problem (ZA version 7.0.483.000). You installed your ZA again... I'm taking a wild guess you downloaded ZA again to install it? Because chances are you installed a newer version that had the July DNS fix in it.
Click to expand...

Actually no, I just reinstalled an old version that I had on disk.
Globetrotter said:
Also, although this is not necessarily relevant to the problem you had, if you can't access the router's configuration IP address in the browser, always check if you have cache/proxy server settings enabled in the browser. Because if you do, then the router's IP address must be added as an Exception in those browser settings otherwise the browser will think it's an external IP address, when it's indeed an internal one on your LAN.
Click to expand...

That's a point; I hadn't thought of that. Don't think it was relevant here, but it's something I'll keep in mind.
 
CathJ said:
Actually no, I just reinstalled an old version that I had on disk.
Click to expand...
Fair enough but I'd still make sure it's not a version prior to 7.0.483.000 because then you can expect DNS errors to occur again in future anyway, since those versions are not patched.
(Overview > Product info in ZA settings to check version)

With regards to the router's IP address, I forgot to mention that if ZoneAlarm for some reason does not grant access to the router, then the router's IP address must be added manually to ZoneAlarm as a Trusted IP address. In future, just shutdown ZA when you troubleshoot DNS errors; easiest way to determine if it's ZA or not.
 
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