{"id":358,"date":"2009-11-25T00:17:37","date_gmt":"2009-11-24T23:17:37","guid":{"rendered":"http:\/\/blog.blackdown.de\/?p=358"},"modified":"2016-10-29T03:51:00","modified_gmt":"2016-10-29T01:51:00","slug":"speedport-routers-eat-your-dns-soa-requests-in-modem-mode","status":"publish","type":"post","link":"https:\/\/blackdown.de\/articles\/speedport-routers-eat-your-dns-soa-requests-in-modem-mode\/","title":{"rendered":"Speedport Routers Eat Your DNS SOA Requests in Modem-Mode"},"content":{"rendered":"

Some years ago I switched to using a Speedport W701V from Deutsche Telekom<\/a> on my ADSL line at home. I set it up in modem-mode and let a small Linux box handle everything else. This setup had worked fine with other modems but shortly after switching to the Speedport I noticed that my local caching DNS server didn’t work correctly anymore. I didn’t really connect the dots at this point, though.<\/p>\n

That happened a few days later when I tried to use Apple’s Back to My Mac<\/em> \u2014 it just didn’t work. After some network tracing I found out that the Apple machine sent DNS SOA requests but never got a reply back. It turned out that all SOA request got blocked somewhere. Sending requests to my own name server (host -t soa blackdown.de ns.blackdown.de<\/code>) and tracing DNS there showed that no packet ever arrived.<\/p>\n

I put the Speedport back into router-mode at this point and, who would have guessed it, SOA requests worked fine again.<\/p>\n

After fruitless discussions with Deutsche Telekom support (it was impossible to find anyone who even remotely understood what I was talking about) and sending a bug report to AVM<\/a> (the 701V actually is a FRITZ!Box) which never got an answer, I finally solved the problem by putting a Freetz<\/a> firmware on the Speedport. This firmware had an option to disable the PPPoE-Filter<\/em>. After disabling the filter the device worked flawlessly in modem-mode.<\/p>\n

Now, a few days ago, I switched to VDSL and got a new router: a Speedport W920V.
\nFirst thing I did was to put it into modem-mode. And there it was again, the DNS SOA problem!<\/p>\n

Knowing what the problem was, I found a simpler fix this time:<\/p>\n

    \n
  1. Download the configuration from the device<\/li>\n
  2. Manually change dnsfilter_for_active_directory = yes;<\/code> to dnsfilter_for_active_directory = no;<\/code> in the pppoefw<\/code> section<\/li>\n
  3. Manually change ipnetbiosfilter = yes;<\/code> to ipnetbiosfilter = no;<\/code> in the pppoefw<\/code> section<\/li>\n
  4. Insert a NoChecks=yes<\/code> line after the Country=<\/code>… line in the header to make the device accept the modified file although its checksum is wrong now<\/li>\n
  5. Upload the modified configuration to the device<\/li>\n<\/ol>\n

    (If you have a local NTP server, you also might want to add it to the server_list<\/code> in the ntpclient<\/code> section while editing the configuration of the Speedport.)<\/p>\n","protected":false},"excerpt":{"rendered":"

    Some years ago I switched to using a Speedport W701V from Deutsche Telekom on my ADSL line at home. I set it up in modem-mode and let a small Linux box handle everything else. This setup had worked fine with other modems but shortly after switching to the Speedport I noticed that my local caching
    [→     Read the rest of this entry<\/a>]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"spay_email":"","jetpack_publicize_message":"","jetpack_is_tweetstorm":false,"jetpack_publicize_feature_enabled":true},"categories":[6,7],"tags":[54,60,61,56,58,53,59,62,57,52,55],"yoast_head":"\n\n\n\n\n\n\n\n\n\n\n\n\n\t\n\t\n\t\n