Author Topic: Advice: Avast conflicting with Windows 7 DNS - Unable to load webpages  (Read 2817 times)

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Offline rykenna

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I'm wondering if anyone has any setting suggestions.

All of a sudden the other day I suddenly couldn't connect to the internet on my server running Windows 7. Win 7 Network diagnostics came back with "Your computer appears to be correctly configured but the device resource DNS is not responding".

I went through everything to fix it, flushing DNS's, changing DNS IP's, restarting server, router etc etc. Until, I turned Avast off and bam... It just started working like that. Turn it back on and I can't resolve any outbound DNS.

Does anyone have an idea as to why this might be? Would turning off the Avast firewall help? As my Windows 7 firewall is active. Just so strange how suddenly it's interfering...

It's never happened in the 6 or so months of running Avast, I've made no changes to the system settings myself.

Thanks

Offline Asyn

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Try to disable RealSite.
Win 8.1 [x64] - Avast PremSec 21.11.6787.IBC [UI.681] - EEK - Firefox ESR 91.3 [NS/uBO/PB] - TB 91.3.2
Avast-Tools: Secure Browser 96.0 - Cleanup 21.4 - SecureLine 5.14 - Driver Updater 21.4 - CCleaner 5.87
Avast Wissenswertes (Downloads, Anleitungen & Infos): https://forum.avast.com/index.php?topic=60523.0

Offline Mark12547

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Do you use TCP Optimizer? If so, on the "Advanced Settings" tab, you should set the "Host Resolution Priority" at the Windows default. You can click on the "Windows default" radio button on the bottom of the TCP Optimizer screen to see what they are.

A couple of years ago I learned the hard way that allowing TCP Optimizer to set these values at the "Optimal" setting causes a conflict with the "Real Site" component of Avast and prevented DNS resolution. My educated guess is that having such high priorities (low numbers) for the priorities caused a race condition with the "Real Site" component, so most DNS requests ended up not being processed or processed at a snail's pace.

At that time I jotted down the default settings, then chose optimal and set them, rebooted, then set custom and changed the "Host Resolution Priority" numbers back to the Windows default, saved and rebooted, and that seemed to work fine with Avast's "Safe DNS", which is now called "Real Site".
« Last Edit: May 17, 2017, 10:34:55 AM by Mark12547 »

Offline rykenna

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Okie doke - I'll take a look at those. Thanks all

Offline Asyn

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You're welcome, report back.
Win 8.1 [x64] - Avast PremSec 21.11.6787.IBC [UI.681] - EEK - Firefox ESR 91.3 [NS/uBO/PB] - TB 91.3.2
Avast-Tools: Secure Browser 96.0 - Cleanup 21.4 - SecureLine 5.14 - Driver Updater 21.4 - CCleaner 5.87
Avast Wissenswertes (Downloads, Anleitungen & Infos): https://forum.avast.com/index.php?topic=60523.0

Offline rykenna

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Well, I had a good hard look. And I can't seem to find any form of advanced settings, or anything that gives me control over TCP. But since I started avast up again, I can connect to the internet okay. But my Windows does still whine about DNS being affected. I'm going to do a reboot and see how it begins behaving. I am convinced they are still directly linked.

Since the last update I'd say a few months back, the Avast interface has had an update to the sleeker looking version (I use the free version). Is there a chance they've removed access to those user settings you mention?

Offline Asyn

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Since the last update I'd say a few months back, the Avast interface has had an update to the sleeker looking version (I use the free version).
The free version does neither include a FW nor RealSite.

- Which Avast..? (Free/Pro/IS/Premier)
- Which version..?
- OS..? (32/64 Bit..? - which SP/Build..?)
- Other security related software installed..?
- Which AV(s) did you use before Avast..?
Win 8.1 [x64] - Avast PremSec 21.11.6787.IBC [UI.681] - EEK - Firefox ESR 91.3 [NS/uBO/PB] - TB 91.3.2
Avast-Tools: Secure Browser 96.0 - Cleanup 21.4 - SecureLine 5.14 - Driver Updater 21.4 - CCleaner 5.87
Avast Wissenswertes (Downloads, Anleitungen & Infos): https://forum.avast.com/index.php?topic=60523.0

Offline rykenna

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- Which Avast..? = Free
- Which version..? = 17.4.2294 (Build 17.1.3394.0)
- OS..? (32/64 Bit..? - which SP/Build..?) = Windows 7 Ultimate SP1 64 bit
- Other security related software installed..? = Nope
- Which AV(s) did you use before Avast..? = None

It seems to be still working after a reboot. But there was definitely a correlation between me disabling Avast and regaining access to the internet without timing out with a DNS issue. I suppose you could consider my case resolved. So I wouldn't waste your time on me. Unless it happens again in which case I'll be back... I'm hoping it was some sort of bug. I was just curious to see if anyone else had experienced anything similar.

Offline Asyn

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OK, you're welcome.
Win 8.1 [x64] - Avast PremSec 21.11.6787.IBC [UI.681] - EEK - Firefox ESR 91.3 [NS/uBO/PB] - TB 91.3.2
Avast-Tools: Secure Browser 96.0 - Cleanup 21.4 - SecureLine 5.14 - Driver Updater 21.4 - CCleaner 5.87
Avast Wissenswertes (Downloads, Anleitungen & Infos): https://forum.avast.com/index.php?topic=60523.0