Using degraded feature set TCP instead of UDP for DNS server

networking ubuntu wireless-networking dns connection

5,215

I had advised doing the following:

Set DNSSEC=no in /etc/systemd/resolved.conf
Use another DNS server than that of the ISP (such as Google Public DNS)
Disable IPv6 in the local network (is perhaps not helpful).

The poster has reported doing this:

I have set DNSSEC=no (commenting it out) through the command:
sudo nano /etc/systemd/resolved.conf
After that the cmd:
sudo systemctl restart systemd-resolved.service
with a reboot.

For changing the DNS servers, the poster has followed the article
How to Set DNS Nameservers on Ubuntu 18.04.

For the moment, the poster's system seems stable.

5,215

Siderius

This is my old stackexchange profile.

Updated on September 18, 2022

Comments

Siderius almost 2 years
I periodically experience a disconnection with my laptop. The connection period lasts about 3-6 minutes. I know for certain that the WiFi works fine.

Using the command sudo journalctl --since="-2 minutes" I find that a recurring line is:
```
(...) Using degraded feature set UDP instead of TCP for DNS server 10.64.10.16.
```
What should I do ? I cannot work since the connection conditions are definitely unstable. I have recently noticed that it is a quite common problem.

I have ubuntu whose version is 21.04, and my laptop is an Acer Aspire 3 A315-56 with a WiFi connection.
- telcoM almost 3 years
  
  Your DNS resolver (maybe systemd-resolved?) might be normally using DNSSEC/EDNS0, and using a TCP connection to DNS server because of this. When you have a connection problem, it notices TCP connection is failing and reverts to UDP and basic DNS protocol. But if you still experience a disconnection, that probably means the reversion to UDP is not helping, perhaps because the actual connection to the destination website (or whatever) still uses TCP and still fails. What is your basis for the conclusion that WiFi works fine? (I'm asking to exactly identify the known-good element(s).)
- harrymc almost 3 years
  
  Things to try: (1) Use another DNS server than that of your ISP (example), (2) Disable IPv6 in your local network, (3) Set DNSSEC=no in /etc/systemd/resolved.conf.
- Siderius almost 3 years
  
  @telcoM I can observe a download plot from another machine. This download is continuous with a constant download speed of 80 kb/s (which is the expected speed). In this way I can observe hypothetical WiFi crashes if any.
- Siderius almost 3 years
  
  I have noticed that resolvconf was missing. After that, as @harrymc suggested I have set DNSSEC=off (commenting it out) through the command: sudo nano /etc/systemd/resolved.conf After that the cmd sudo systemctl restart systemd-resolved.service
- harrymc almost 3 years
  
  Did this change anything? (Or you don't know yet)
- Siderius almost 3 years
  
  @harrymc partially. The connection tends to be a little more stable but I always experience periodic crashes in the connection
- harrymc almost 3 years
  
  Try also the other points in my comment, to see if they change something.
- Siderius almost 3 years
  
  @harrymc I haven't experienced any crash. Put is as an answer. I would recommend this [link] (linuxize.com/post/how-to-set-dns-nameservers-on-ubuntu-18-0‌4) as a dns change guide rather than your aforementioned link.