Score:4

DNS lookup issues only in specific network

cz flag

I am running Ubuntu 20.04 on my work computer and I have a few issues when working from home.

When I am at the office, I can browse the internet without issues. However, when I decide to work from home there are some sites (like github.com) that simply do not work.

$ nslookup www.github.com
;; connection timed out; no servers could be reached

This is specific to my computer, as all the other devices in the house can access these "problematic" domains. If I really need to access the website, I create a Wi-Fi hotspot using my phone and connect my work computer to it.

Additionally, sometimes the lookup is successful and I manage to get a few precious seconds of connectivity, but this seems to be completely random.

Anyway, I searched around for some time and the only thing that makes sense for me is that this is due to DNS issues. I tried forcing my PC to use Google's DNS Servers, but the problem persists.

Can anyone shed a light on this problem?

aq flag
When you say 'work from home' are you on a. work VPN?
cz flag
No VPN. Just my regular home network.
Hasan Ali avatar
in flag
Did you try using a VPN at home?
aq flag
post the output of `nmcli device show <device> | grep DNS` where <device> is your network device like `eth0`
Score:2
pl flag

It is likely a DNS problem. Try diagnosing with a few commands, and please post the output in the question, verbatim, and as text (not screen capture). To check connectivity

$ ping 8.8.8.8

Then

$ cat /etc/resolv.conf

and compare with another working Ubuntu if possible. Then

$ sudo tcpdump -n -i wlp0s20f3 host 8.8.8.8

and from another terminal

$ dig @8.8.8.8 www.google.com

and check what response you get in the first one. Ref. If you get something like

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on wlp0s20f3, link-type EN10MB (Ethernet), capture size 262144 bytes
10:40:11.448275 IP 192.168.0.139.58832 > 8.8.8.8.53: 35577+ [1au] A? www.google.com. (55)
10:40:11.466551 IP 8.8.8.8.53 > 192.168.0.139.58832: 35577 1/0/1 A 172.217.172.68 (59)

that means you are transmitting and receiving. If you don't get the last line, you are not receiving.

cz flag
Yup. It was a DNS issue that somehow only affected my computer. I had to change the DNS servers for my mesh network through the vendor app.
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