Very slow DNS lookup

Question

I'm on Ubuntu 16.04 LTS, and when I visit a website/curl/wget/ping/etc anything that isn't an IP address, it takes an annoyingly long time (> 5 s), whereas anything directly using an IP address is pretty much instant (< 10 ms, as one would expect).

When I cat /etc/NetworkManager/NetworkManager.conf, I get:

[main]
plugins=ifupdown,keyfile,ofono
dns=dnsmasq

[ifupdown]
managed=false

I've tried changing to #dns=dnsmasq, but it didn't have any noticeable effect.

cat /etc/network/interfaces is also quite basic:

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

A bit odd is cat /etc/resolv.conf:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN

nameserver 10.63.240.10
nameserver 127.0.1.1
search $companydomain$.com

The nameserver 10.63.240.10 is something a colleague doesn't have, and is the only way in which the above 3 files differ for us. I suspect that is the root of the issue, because when I do host www.stackexchange.com 10.63.240.10, I get:

;; connection timed out; no servers could be reached

Commenting it out and restarting the network-manager fixes the issue temporarily, only to return upon rebooting.

I've also noticed in the Network Connections menu, two (seemingly) auto-generated Bridge entries are listed: br-8f98800bd128 and br-bd749c12d64c. If I delete these, they're back after a reboot. My aforementioned colleague doesn't have these either.

I've also tried the suggestions from How do I configure my DNS settings in Ubuntu server? and Extrememly slow DNS lookup, but the issue remains.

Per M. Becerra's suggestion, I ran sudo updatedb; locate 10.63.240.10. This didn't give me any output.

Mikael Schultz suggested I do nmcli device show, which outputs:

GENERAL.DEVICE:                         br-8f98800bd128
GENERAL.TYPE:                           bridge
GENERAL.HWADDR:                         02:42:50:5E:58:3B
GENERAL.MTU:                            1500
GENERAL.STATE:                          100 (connected)
GENERAL.CONNECTION:                     br-8f98800bd128
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveConnection/2
IP4.ADDRESS[1]:                         172.18.0.1/16
IP4.GATEWAY:                            
IP6.GATEWAY:                            

GENERAL.DEVICE:                         br-bd749c12d64c
GENERAL.TYPE:                           bridge
GENERAL.HWADDR:                         02:42:B1:85:6D:E3
GENERAL.MTU:                            1500
GENERAL.STATE:                          100 (connected)
GENERAL.CONNECTION:                     br-bd749c12d64c
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveConnection/3
IP4.ADDRESS[1]:                         172.19.0.1/16
IP4.GATEWAY:                            
IP6.GATEWAY:                            

GENERAL.DEVICE:                         docker0
GENERAL.TYPE:                           bridge
GENERAL.HWADDR:                         36:CA:3D:66:B7:03
GENERAL.MTU:                            1500
GENERAL.STATE:                          100 (connected)
GENERAL.CONNECTION:                     docker0
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveConnection/1
IP4.ADDRESS[1]:                         172.17.0.1/16
IP4.GATEWAY:                            
IP6.GATEWAY:                            

GENERAL.DEVICE:                         wlp3s0
GENERAL.TYPE:                           wifi
GENERAL.HWADDR:                         00:28:F8:9C:2A:4D
GENERAL.MTU:                            0
GENERAL.STATE:                          100 (connected)
GENERAL.CONNECTION:                     Crowdynews
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveConnection/0
IP4.ADDRESS[1]:                         10.0.0.27/24
IP4.GATEWAY:                            10.0.0.1
IP4.ROUTE[1]:                           dst = 169.254.0.0/16, nh = 0.0.0.0, mt = 1000
IP4.DNS[1]:                             8.8.8.8
IP4.DNS[2]:                             8.8.4.4
IP4.DOMAIN[1]:                          crowdynews.com
IP6.ADDRESS[1]:                         fe80::9264:b967:1c59:3e50/64
IP6.GATEWAY:                            

GENERAL.DEVICE:                         enp4s0
GENERAL.TYPE:                           ethernet
GENERAL.HWADDR:                         C8:5B:76:F1:1C:EC
GENERAL.MTU:                            1500
GENERAL.STATE:                          20 (unavailable)
GENERAL.CONNECTION:                     --
GENERAL.CON-PATH:                       --
WIRED-PROPERTIES.CARRIER:               off

GENERAL.DEVICE:                         lo
GENERAL.TYPE:                           loopback
GENERAL.HWADDR:                         00:00:00:00:00:00
GENERAL.MTU:                            65536
GENERAL.STATE:                          10 (unmanaged)
GENERAL.CONNECTION:                     --
GENERAL.CON-PATH:                       --
IP4.ADDRESS[1]:                         127.0.0.1/8
IP4.GATEWAY:                            
IP6.ADDRESS[1]:                         ::1/128
IP6.GATEWAY:

ip address prints:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
   valid_lft forever preferred_lft forever
inet6 ::1/128 scope host 
   valid_lft forever preferred_lft forever
2: enp4s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
link/ether c8:5b:76:f1:1c:ec brd ff:ff:ff:ff:ff:ff
3: wlp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 00:28:f8:9c:2a:4d brd ff:ff:ff:ff:ff:ff
inet 10.0.0.27/24 brd 10.0.0.255 scope global dynamic wlp3s0
   valid_lft 1660731sec preferred_lft 1660731sec
inet6 fe80::9264:b967:1c59:3e50/64 scope link 
   valid_lft forever preferred_lft forever
4: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
link/ether 02:42:f3:cd:08:8c brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
   valid_lft forever preferred_lft forever
5: br-8f98800bd128: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
link/ether 02:42:50:5e:58:3b brd ff:ff:ff:ff:ff:ff
inet 172.18.0.1/16 brd 172.18.255.255 scope global br-8f98800bd128
   valid_lft forever preferred_lft forever
6: br-bd749c12d64c: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
link/ether 02:42:b1:85:6d:e3 brd ff:ff:ff:ff:ff:ff
inet 172.19.0.1/16 brd 172.19.255.255 scope global br-bd749c12d64c
   valid_lft forever preferred_lft forever

cat /etc/resolvconf/resolv.conf.d/head:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN

nameserver 10.63.240.10

cat /etc/resolvconf/resolv.conf.d/base generates no output.

How do I fix this?

Try to change to a name server like `8.8.8.8` - Side note: https://whois.domaintools.com/10.63.240.10 — M. Becerra, May 29 '18 at 11:06
I've tried adding a line with `dns-nameservers 8.8.8.8` in /etc/network/interfaces, but that didn't fix it, because `10.63.240.10` was still tried first. — Ghost, May 29 '18 at 11:32
Please comment out the original name server to let `8.8.8.8` be used — M. Becerra, May 29 '18 at 11:52
Where? Removing `nameserver 10.63.240.10` from `/etc/resolv.conf` and then manually restarting the network-manager only works temporarily. It's back after a reboot. I can't find where it keeps coming from, but it always returns. — Ghost, May 29 '18 at 11:59
Sorry I meant `sudo grep -r "10.63.240.10" /*`.Also try to comment out the current name server at `/etc/resolv.conf` by editing it like this `# nameserver 10.63.240.10` and then append `nameserver 8.8.8.8` — M. Becerra, May 29 '18 at 13:04
As mentioned, commenting out `nameserver 10.63.240.10` from `/etc/resolv.conf` seems to work, but a reboot reinstates the problem. — Ghost, May 29 '18 at 14:19
Could you edit your answer with the output of the command `nmcli device show`? And also the output of the command `ip address`. — , May 29 '18 at 19:15
Nice, but it looks okay to me. Can you also insert the output of `cat /etc/resolvconf/resolv.conf.d/head` and `cat /etc/resolvconf/resolv.conf.d/base`? — , May 31 '18 at 16:46

score 3 · Accepted Answer · answered Jun 08 '18 at 17:20

3

The problem seems to be that there is a faulty DNS server in the file /etc/resolvconf/resolv.conf.d/head.

Edit the head file and delete the line that says nameserver 10.63.240.10 and you should have solved your problem.

Run sudo nano /etc/resolvconf/resolv.conf.d/head from the Terminal to edit the file and make sure that the only content of the file is:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN

Hope this solves your problem.

answered Jun 08 '18 at 17:20

It seems your suggestion worked. Should this be a permanent solution? Because it even says in the file any modifications will be overwritten. I've rebooted, but that didn't seem to restore the file to the version with `nameserver 10.63.240.10`, so DNS requests are still quick. :) Do you have any idea where the custom DNS server might've come from? As far as I know, I haven't set it myself, and I'm the only one who's installed anything on this laptop. Could it have been set by some network settings? – Ghost Jun 11 '18 at 10:21
I would consider it a permanent solution. If it isn’t I’m sure someone will object :) It should not have been there in the first place and I have no idea how it got there. These (head and base) are the files that will be the source of the file /etc/resolv.conf when it is generated, that is why the text is saying that modifications will be overwritten. – Jun 11 '18 at 11:17
Aha, so the `# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN` line is only in the `/etc/resolv.conf.d/head` file so it finds its way into the regular `/etc/resolv.conf` file? Thanks! – Ghost Jun 11 '18 at 15:08
Yes that is my understanding. No problem :) – Jun 11 '18 at 17:33

score 1 · Answer 2 · answered May 01 '19 at 04:06

I had the same problem. To solve it, I changed my DNS server settings and now everything gets resolved really fast (apt update, Firefox startup, git, etc.).

Change DNS server settings:

If you are using a wired network, go to Ubuntu Settings > Network > Wired > Options > IPv4. Make sure IPv4 Method is Automatic (DHCP) and choose your DNS server (I personally use https://1.1.1.1/dns/). You can do the same for IPv6, make sure to put a valid IPv6 to the DNS server.

If you are using a Wireless connection, go to Ubuntu Settings > Wireless > [YourWifi] > Options and follow the same instructions.

OP seems to like using terminal, the equivalent way is [using `nmtui` (NetworkManager TUI)](https://askubuntu.com/a/1174193/349837) — Pablo Bianchi, Sep 14 '19 at 19:03

score 1 · Answer 3 · answered Mar 28 '23 at 12:14

1

Meybe this can help someone (THE PROBLEM IS THE DOCKER). I had the same problem on UBUNTU 22.04, after a long time changing network related configs the solutions was.

docker network prune

I had a lot of docker networks and this was causing a slow DNS Lookup (I could reach some sites and others was giving timeout)

answered Mar 28 '23 at 12:14

Bodok

111
3

Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Mar 29 '23 at 10:36

Very slow DNS lookup

3 Answers3

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