DNS Resolver Slow/Broken?

RouterOS General
1

I’m using Audience and I’m investigating why initial page load seems to be so slow. It seems that the RouterOS DNS server is slow and/or missing queries.

Relevant config snippets:

/system routerboard print
       routerboard: yes
        board-name: Audience
             model: RBD25G-5HPacQD2HPnD
     serial-number: BB0C0B6B7926
     firmware-type: ipq4000
  factory-firmware: 6.45.4
  current-firmware: 6.48.3
  upgrade-firmware: 6.48.3
/ip dhcp-client
add comment=defconf disabled=no interface=ether1 use-peer-dns=no use-peer-ntp=no
/ip dhcp-server network
add address=172.16.44.0/24 dns-server=172.16.44.1 gateway=172.16.44.1 netmask=24
/ip dns
set allow-remote-requests=yes max-concurrent-queries=1000 max-concurrent-tcp-sessions=200 query-server-timeout=200ms servers=8.8.8.8,8.8.4.4

The symptom is that many page loads stall at first for ~1-2 seconds before finally loading, and occasionally Chrome reports that a page cannot be resolved at all, and then immediately (~1s) automatically reloads and it works.

At first I suspected that my ISP was intercepting DNS traffic and performing some trickery. But if I set my computer manually to use Google Honest DNS (bypassing the RouterOS DNS resolver), there are no problems.

Additionally, if I change the RouterOS DHCP config to give Google Honest DNS addresses to the clients instead of using the RouterOS resolver, the problems are also solved.

Therefore, I can only conclude that there is a problem with the RouterOS DNS resolver.

I have no firewall rules that would affect DNS.

Has anyone else noticed this problem lately?

2

Why you have the nice idea to short DNS query timeout from 2 seconds to 0,2 seconds?
(and default max-concurrent-queries from 100 to 1000 and max-concurrent-tcp-sessions from 20 to 200?)

If you put random numbers on config, you must expect random behavior.

3

Aha, thanks for noticing that. I made these changes in an attempt to figure out the problem.

The changes are not the cause of the problem, but I will revert those settings to default.

4

FYI, I have solved this problem on a different network and router (hap ac3) by doing the same thing: using DHCP to push Google Honest DNS directly to the clients instead of using the RouterOS resolver.

There is definitely something wrong with the Router OS DNS resolver.

5

Couldn’t help but notice DNS resolver fixes in the 6.48.4 release.

I haven’t reverted back to the internal resolver yet, but I will soon and report back.

6

Was it ever determined if the RouterOS resolver has an issue? I’m experiencing the slowness/delay, as well.

7

I forgot to report back. I went back to the internal resolver on 6.48.4 about 10 days ago and it has been working fine for me now.

8

I had same problem! Memory was full. I had zeroes in red square on picture. I had to delete everything I could delete from internal flash manually. 100KB was freed. After that I reset mikrotik. And problem solved!