Abnormally slow speeds downloading from Steam

I had the same problem and the dnsmasq solution did not work for me, neither did changing download server or set a download limit. I hope this will help others in the future:

The problem for me was that my steam folder was on a mounted ntfs partition with sync enabled (check /etc/fstab). That throttles write-speed significantly. Change sync to async and I have normal writing speeds which means Steam can download at full speed, too.

Might be a silly suggestion but have you tried going into Settings and checking whether there's a bandwidth download limit set on your account?

It's found under the Downloads tab. Once clicked, there should be a little dropdown menu.

On Linux Mint Cinnamon 19 (and possibly most of Ubuntu based OS) :

In a terminal :

sudo nano /etc/sysctl.conf

In nano editing add this lines at the bottom of the file :

net.ipv6.conf.all.disable_ipv6 = 1

net.ipv6.conf.default.disable_ipv6 = 1

net.ipv6.conf.lo.disable_ipv6 = 1

Save and close

In the terminal :

sudo sysctl -p

Sources : https://forums.linuxmint.com/viewtopic.php?t=210093

I found another solution to installing dnsmasq. You use unbound instead.

# apt-get install unbound # do this first or you'll be sad
# cd /etc/NetworkManager
# service NetworkManager stop
# vi NetworkManager.conf # or whatever editor you want; I don't care
[change "dns=dnsmasq" to "dns=unbound"]
# rm /etc/resolv.conf # don't forget this
# service NetworkManager start

This would tell DNS queries to go through your local unbound server (at 127.0.0.1 a.k.a. localhost), retries over TCP should work as expected, and Steam should be able to download just fine. You can test it with:

# nslookup cdn.comcast.cs.steampowered.com

This, together with marts' answer helped me solve this issue. For a better explaination of why the above works, see this post.

I just fixed my issue with this. What I did was

sudo systemctl disable systemd-resolved
sudo systemctl stop systemd-resolved

and then

sudo systemctl enable systemd-resolved
sudo systemctl start systemd-resolved

I don't know how this works but it did.

The slow download speeds could also be, if you are using a dual-boot system, the way that the ntfs partition is mounted could also result in the download taking forever. Assuming you are downloading the games to your ntfs partition. As it has to download and simultaneously transfer the data to the partition(if you are using the mount argument sync).

If you are using a dual-boot system and are experiencing slow download speeds, also consider this as a possibility. Changing your 'auto-mount' settings in /etc/fstab could make a difference. Here is the answer I am basing this on: Very slow write rate from ext4 to NTFS. And the fact that it was the case for me.

As a side note, here is how to setup the partitions to auto mount.