Very slow DNS lookup

16.04 networking network-manager dns

14,715

Solution 1

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.

Solution 2

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.

14,715

Ghost

Updated on September 18, 2022

Comments

Ghost over 1 year

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?

M. Becerra almost 6 years

Try to change to a name server like 8.8.8.8 - Side note: whois.domaintools.com/10.63.240.10
Ghost almost 6 years

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.
M. Becerra almost 6 years

Please comment out the original name server to let 8.8.8.8 be used
Ghost almost 6 years

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 almost 6 years

Done. It didn't give me any output...
M. Becerra almost 6 years

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
Ghost almost 6 years

As mentioned, commenting out nameserver 10.63.240.10 from /etc/resolv.conf seems to work, but a reboot reinstates the problem.
Admin almost 6 years

Could you edit your answer with the output of the command nmcli device show? And also the output of the command ip address.
Ghost almost 6 years

Of course. See above for edits. :)
Admin almost 6 years

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?
Ghost almost 6 years

I've added both. resolv.conf.d/base is empty.

Ghost almost 6 years

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?
Devin almost 6 years

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.
Ghost almost 6 years

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!
Devin almost 6 years

Yes that is my understanding. No problem :)
Pablo Bianchi over 4 years

OP seems to like using terminal, the equivalent way is using nmtui (NetworkManager TUI)