Recently my Ubuntu 18 laptop had intermittent very slow internet/network. After checking the usual causes (router, WiFi, etc.), I found this helpful article. Turns out what fixed it was one of those suggestions.
Edit this file:
sudo vi /etc/nsswitch.conf
Then change the line that says:
hosts: files mdns4_minimal [NOTFOUND=return] dns mdns
To this:
hosts: files dns mdns4_minimal [NOTFOUND=return] mdns
So, in hindsight, it seems to have been a DNS problem.
Update 1
While this seemed to fix the problem temporarily, network problems started again. After an hour or two of reading about the issue, I made another change. I learned that Ubuntu 18 changed the way network is configured, using a new service called “netplan”. The /etc/netplan directory should have config files, but mine was empty! I don’t know how it got emptied; I certainly didn’t do it. But I needed to create a default config file. I created a file called 01-netcfg.yaml:
network: version: 2 renderer: networkd # ethernets: # wlan0: # dhcp4: true # nameservers: # addresses: [192.168.1.1]
After some experimentation I commented out the last few lines. This tells Ubuntu that the network manager service will control network. Then I configured it in the network WiFi GUI, enabling DHCP wasn’t enough; I also added my home router (192.168.1.1) to the DNS list.
Networking (more specifically, DNS resolution) was still slow and occasionally intermittent. Finally, I had to flush the DNS cache:
sudo systemd-resolve --flush-caches
Now, everything seems to be working again.
Update 2
This too only fixed things temporarily. I still was getting intermittent network problems – but only on WiFi, not when wired. It looks like Ubuntu 18’s new “netplan” was conflicting with the “networking” service. I configured netplan and stopped the networking service. That is:
In the /etc/netplan directory, I had this file named 10-netcfg.yaml, which tells the system that the desktop Network Manager app will control network setup:
network: version: 2 renderer: NetworkManager
I created additional files AFTER the ones that are there, so they override this. These files look like this:
20-wlan0.yaml
# Enable this only if you don't want to use the desktop GUI
network:
ethernets:
wlan0:
addresses: []
dhcp4: true
optional: true
version: 2
30-eth0.yaml
# Enable this only if you don't want to use the desktop GUI
network:
ethernets:
wlan0:
addresses: []
dhcp4: true
optional: true
version: 2
Because they sort after the first file, they override it. Next, run this command:
mclement@clements6:~$ sudo netplan --debug generate DEBUG:command generate: running ['/lib/netplan/generate'] ** (generate:27016): DEBUG: 09:12:23.854: Processing input file /etc/netplan/10-netcfg.yaml.. ** (generate:27016): DEBUG: 09:12:23.854: starting new processing pass ** (generate:27016): DEBUG: 09:12:23.854: Processing input file /etc/netplan/20-wlan0.yaml.. ** (generate:27016): DEBUG: 09:12:23.854: starting new processing pass ** (generate:27016): DEBUG: 09:12:23.854: Processing input file /etc/netplan/30-eth0.yaml.. ** (generate:27016): DEBUG: 09:12:23.854: starting new processing pass ** (generate:27016): DEBUG: 09:12:23.854: wlan0: setting default backend to 2 ** (generate:27016): DEBUG: 09:12:23.854: Configuration is valid ** (generate:27016): DEBUG: 09:12:23.854: eth0: setting default backend to 2 ** (generate:27016): DEBUG: 09:12:23.854: Configuration is valid ** (generate:27016): DEBUG: 09:12:23.855: Generating output files.. ** (generate:27016): DEBUG: 09:12:23.855: networkd: definition wlan0 is not for us (backend 2) ** (generate:27016): DEBUG: 09:12:23.855: networkd: definition eth0 is not for us (backend 2)
Note the last 2 lines, which is “networkd” saying it won’t be managing these network connections.
Next, apply this configuration
mclement@clements6:~$ sudo netplan apply
Now, disable the system networking service
sudo service networking stop
At this point, my WiFi networking started working again, and was not slow anymore.
Update 3
Sigh… this again was only a temporary fix. Even after all of the above, network was still slow! Then I remembered that I was using 5 GHz WiFi, which has different frequencies/channels in different regions, so requires the device to know what country it is in. So I changed one more thing. Edit the file /etc/default/crda and set my country code. That is, the file originally looked like this:
# Set REGDOMAIN to a ISO/IEC 3166-1 alpha2 country code so that iw(8) may set # the initial regulatory domain setting for IEEE 802.11 devices which operate # on this system. # # Governments assert the right to regulate usage of radio spectrum within # their respective territories so make sure you select a ISO/IEC 3166-1 alpha2 # country code suitable for your location or you may infringe on local # legislature. See `/usr/share/zoneinfo/zone.tab' for a table of timezone # descriptions containing ISO/IEC 3166-1 alpha2 country codes. REGDOMAIN=
Note that REGDOMAIN was not set. I changed that last line to this:
REGDOMAIN=US
Since “US” is the code for my country.
What is interesting, is that I tested and 2.4 GHz WiFi worked fine all along. It was only 5 GHz WiFi that was intermittently broken. This would be consistent with not having the region set.
Given all this, I reverted the netplan changes above, so the desktop NetworkManager controls my networking.
Update 4
Again, this still didn’t fix the problem. However, the problem may have been the channel I was using on 5 GHz. This thread was helpful. Channel 149 was listed by “iw list”, but not by “iwlist chan”. I changed the router to use channel 48, which appears in both lists, and it is now working.
Conclusion
There’s a lot here, some of which wasn’t necessary. In summary, the fix was:
Configure /etc/netplan to tell the desktop Network Manager GUI to manage network connections. This is the default Ubuntu desktop setup.
Set /etc/default/crda to set the system country code (needed for 5 GHz).
Run iw list and iwlist chan to see which 5 GHz channels the WiFi card supports.
Configure my router to use one of these 5 GHz channels.
BANG! It’s still working overnight, fast and reliable. Problem solved.