Slow webpage responses / pings on NixOS

Help
1

Hello, can someone help me debug slow webpages / pings on NixOS.

When I open webpages, it often takes ~20seconds until I get an output. Afterwards everything is pretty fast. I have also ran a speedtest which gave back normal results of 250/50.

This is what happens when I time a ping command:

[user@nixos:~]$ time ping speedtest.net
PING speedtest.net (151.101.194.219) 56(84) bytes of data.
64 bytes from 151.101.194.219: icmp_seq=1 ttl=59 time=12.4 ms
64 bytes from 151.101.194.219: icmp_seq=2 ttl=59 time=11.9 ms
^C
--- speedtest.net ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 5030ms
rtt min/avg/max/mdev = 11.869/12.125/12.382/0.256 ms

real    0m5,411s
user    0m0,003s
sys    0m0,001s

As you can see, it takes about 5 real time seconds until the first response happens. Can someone help me debug this further, I don’t know where to start. Thank you!

Info about my system:
NixOS 25.05 on stable channel using flakes

2

The ping itself looks okay. Maybe check your DNS settings. If the first DNS server in the list is not reachable then there is typically some delay.

3

This was indeed a DNS issue. I have previously tested DNS and encountered no issues.
I am using adguardhome and some of the queries got dropped due to a ratelimit in the config that is set to 20 by default.

Without the ratelimit, I don’t have this issue anymore. Seems like I just had luck when testing dns so the ratelimit wasn’t reached.