Tag Archive: fix

DNS Dropping / Not Resolving – Draytek 2820 Router

Had an issue the last few weeks where DNS across the network would randomly just drop/timeout for a period of a few minutes to an hour or so.
Across the entire network (at around lunctime) users would suddenly be unable to access certain websites but strangely applications like skype / outlook etc would still function normally.

I quickly diagnosed that it was a DNS issue as normal web browsing would fail but if i entered the domain’s IP address (using my phone and www.ip-lookup.net to find the domain ip) it would load instantly.
I tried bypassing the local DNS server by changing DNS manually to Google DNS (8.8.8.8 and 8.8.4.4) but this also didn’t work while the “blackout” was in progress.

Summary of symptoms…

  • Connection not lost – existing connections stay alive (until bounced/rebooted)
  • Pings to 8.8.8.8 (Google DNS) all successful
  • Unable to resolve DNS through any DNS servers (Local DNS Server, Google DNS, Open DNS, ISP DNS etc) on any machine, laptop, server within the network.
  • nslookup fails with Local DNS server, Google DNS, Open DNS and ISP DNS
  • On router reboot DNS goes back to working OK for a period of time.

Restarting the router (a Draytek Vigor 2820 in this case) would fix the issue but usually DNS resolution would just drop off again sometime after (sometimes a few minutes, sometimes an hour or so).

After much frustration, and the realisation that it had to be something to do with the router, I rooted around in the Draytek Vigor 2820 settings to see what could be causing the DNS to drop off.

The penny dropped when looking at the DOS defence firewall settings. (Firewall > DOS Defence) in particular UDP Flood Defence

The threshold value was set to 150 packets/sec. Draytek recommend 2000 packets/sec for a 20mb connection. So roughly 100 packets/sec for each 1mb
For a more specific calculation see here: http://www.draytek.com/index.php?option=com_k2&view=item&id=5315&Itemid=293&lang=en

This particular connection is at best 8mb to i set this threshold value to 800. (See screengrab below)
dns-dropping-not-resolving-draytek-vigor-2820

I’m guessing everyone on their lunch breaks was hitting the connection hard with youtube, facebook, twitter, random browsing etc triggering the DoS defence filter.

This has now completely solved this incredibly annoying DNS issue.

Hope this helped you. If it did please share on twitter, google plus, facebook etc or donate a little something towards my next caffeine fix by clicking the [Buy me a coffee] PayPal button in the sidebar!)

McAfee Total Protection: As a service virus scan won’t update – McAfee Un-Install Cleanup

The other day I came across a problem while when installing  McAfee Total Protection “as-a-service”  (mcafeeasap.com) on a laptop which had a free trial version of McAfee pre-installed.

Once installed, the Virus scan part of McAfee as a service would say it was  downloading  the latest definitions but would never complete.

The taskbar status icon was grey and would stay greyed out (it’s supposed to be red if all is ok).

After much digging and google searching I came across quite a few methods to try and fix this but none seemed to work.

Here are the steps I took to fix this issue…

McAfee Total Protection Clean Install Procedure…

Follow all of the steps below to fix the issue.

NOTE: Ignore if ANY of the trouble shooting steps below end in failure and continue to proceed with them all in order…

Uninstallation / Cleanup:

1. Log on to your security center at www.mcafeeasap.com

2. Click on the “Utilities” tab-> select the sub tab “Migration & Optimization“.

3. Under the Cleanup Utility –> select the Download option.

4. Download and save it to the desktop then run the downloaded .exe file to uninstall.

5. Delete all entries from Start->Run->temp (usually “C:\windows\temp” depending on how your OS was installed)  – Select all the files and folders and delete them (Ignore any files that you can’t delete)

6. Delete all entries from start->Run->%temp% (This is the user’s temp folder e.g. “C:\Users\Username\AppData\Local\Temp”) – Select all the files and folder under that and delete. (Ignore any files that you can’t delete)

7. Reboot the computer.

BEFORE YOU CONTINUE…  Reset the Windows firewall to default and then disable the windows firewall before you start the installation.

Installation :

To install the updates for the Total Protection Service, use the Silent installation method.

1. Open the webpage www.mcafeeasap.com and login with your details.

2. Click on “Utilities” at the top

3. Under the “Installation” tab, select the second option “Silent installation” to download.

4. save the vssetup.exe file to your c: drive.

5. Now click Start –> type cmd.exe into the search field.

6. Then right-click on cmd.exe and click “Run as administrator” to open the command prompt in admin mode.

7. Type cd\ (and hit the enter key)

6.Type or copy this command and paste

VSSETUP.EXE /CK=012345678901234567890123 /P=VFB

You must put YOUR company key in the above command (replace the numbers after CK=) and then run the command (hit enter).

The letter after the “P” parameter, V is the virus scan, F is the firewall and B the browser protection. If you want to install all these features leave the command as it is. if you don’t want a particualr feature installed you need to remove the letter (V, F or B) from the above command.

Run a complete update from the M shield icon (right click) after the install is done with the above method.

I hope this helps you out.
If it works for you tweet me to say thanks or