Community discussions

MikroTik App
 
Florian
Member Candidate
Member Candidate
Topic Author
Posts: 117
Joined: Sun Mar 13, 2016 9:45 am
Location: France

DNS server stop working from time to time

Mon Mar 06, 2017 10:09 am

Hello,

I've a strange problem with the Mikrotik DNS server of my CCR 1009. The setup is pretty classic :

[admin@MikroTik] > /ip dns print
servers: 80.67.169.12,8.8.8.8
dynamic-servers:
allow-remote-requests: yes
max-udp-packet-size: 4096
query-server-timeout: 2s
query-total-timeout: 4s
max-concurrent-queries: 300
max-concurrent-tcp-sessions: 80
cache-size: 4096KiB
cache-max-ttl: 2d
cache-used: 63KiB

So, all my pc are using the Mikrotik ip address as DNS server, and it's working fine. For a while. Then, all of the sudden, it's not working anymore. The DNS doesn't resole anything, and, if I try a nslookup from one of my windows machine, it's timing out, like the DNS "service" of the mikrotik is crashed. So, 2 "solutions". Either I reboot the router, or I modify something in the config, press apply, and boom, dns is up again.

I've this problem since 6.38. I'm using 6.39rcs now, and the problem is still here. I can be good for weeks, or hours, it's really seems random.

I saw a similar post here from 2013 : viewtopic.php?t=79649 and no solution except using another dns server.

Thx you.
 
jarda
Forum Guru
Forum Guru
Posts: 7756
Joined: Mon Oct 22, 2012 4:46 pm

Re: DNS server stop working from time to time

Mon Mar 06, 2017 10:27 am

Report it to support as a bug.
 
Florian
Member Candidate
Member Candidate
Topic Author
Posts: 117
Joined: Sun Mar 13, 2016 9:45 am
Location: France

Re: DNS server stop working from time to time

Mon Mar 06, 2017 10:58 am

Hi.

Ok, what is the "official" way to submit a bug report ? I can't seem to find it, sorry :/

Thx.
 
User avatar
soonwai
Member Candidate
Member Candidate
Posts: 186
Joined: Mon Feb 06, 2012 10:50 pm
Location: Kuala Lumpur

Re: DNS server stop working from time to time

Mon Mar 06, 2017 6:10 pm

I usually do it via email. Refer here: https://mikrotik.com/support
 
Florian
Member Candidate
Member Candidate
Topic Author
Posts: 117
Joined: Sun Mar 13, 2016 9:45 am
Location: France

Re: DNS server stop working from time to time

Tue Mar 07, 2017 10:05 pm

Yeah, I did it yesterday :) Thx :)
 
User avatar
dgnevans
Member
Member
Posts: 469
Joined: Fri Mar 08, 2013 11:24 am
Location: Zimbabwe
Contact:

Re: DNS server stop working from time to time

Tue Mar 07, 2017 10:12 pm

Are you runsning any interfaces with dhcp client on them there is a similar issue reported by a number of users where by dhcp client dns causes the issue. they found turning off that dns resolved the issue. I am using the ccr1009 for the past 8 months as dns without issue.
 
Florian
Member Candidate
Member Candidate
Topic Author
Posts: 117
Joined: Sun Mar 13, 2016 9:45 am
Location: France

Re: DNS server stop working from time to time

Wed Mar 08, 2017 10:42 pm

I do.

But I found the "true" problem in my case.

I mailed them this : (sorry for my bad english)
"Additional info :

In fact, it seems that Mikrotik sometime doesn't try all the dns servers in the list, but only the last one. And if the last one is down, then, it doesn't try the first one, so DNS failed.

[admin@MikroTik] > /ip dns print
servers: 80.67.169.40,80.67.169.12
dynamic-servers:
allow-remote-requests: yes
max-udp-packet-size: 4096
query-server-timeout: 2s
query-total-timeout: 4s
max-concurrent-queries: 300
max-concurrent-tcp-sessions: 80
cache-size: 4096KiB
cache-max-ttl: 2d
cache-used: 36KiB

In this case, when I'm taping this email, 80.67.169.12 is down. But 169.40 is up. BUT, only 169.12 is "used", so everything failed.

When I switch the 2 servers orders :

[admin@MikroTik] > /ip dns print
servers: 80.67.169.12,80.67.169.40
dynamic-servers:
allow-remote-requests: yes
max-udp-packet-size: 4096
query-server-timeout: 2s
query-total-timeout: 4s
max-concurrent-queries: 300
max-concurrent-tcp-sessions: 80
cache-size: 4096KiB
cache-max-ttl: 2d
cache-used: 30KiB

It's working again, because 169.40 is used, and not 169.12. Which is the correct thing, but, it seems it doesn't even try the first servers, only hitting the last one, even if it doesn't work.

Even when the 2 servers are working, often only the last one is used. So their is not real redundancy here... Joined the supout.rif file this time.

Thx !"
 
TheLordOfTheShells
Frequent Visitor
Frequent Visitor
Posts: 71
Joined: Tue Oct 03, 2017 2:48 am

Re: DNS server stop working from time to time

Fri Mar 19, 2021 10:12 am

Hi
I have the same issue after upgrading our CRS1036 to v6.48.1. The internet on router is still active and I can ping to 8.8.8.8 or 8.8.4.4 but end-client does not.
So I have to change DNS server to work, It quite strange after awhile the new DNS server also can not reached on client side.
Reboot will make it work again.
 
boocko
just joined
Posts: 3
Joined: Mon Feb 01, 2021 5:37 pm

Re: DNS server stop working from time to time

Tue Oct 05, 2021 10:32 am

Hi
I have the same issue after upgrading our CRS1036 to v6.48.1. The internet on router is still active and I can ping to 8.8.8.8 or 8.8.4.4 but end-client does not.
So I have to change DNS server to work, It quite strange after awhile the new DNS server also can not reached on client side.
Reboot will make it work again.
Similar here with RB4011 v v6.48.3. Sometimes even without reboot it starts working again after some time. My solution is to put a backup external DNS server to clients (via DHCP, primary is MT DNS, secondary is external).

Who is online

Users browsing this forum: Amazon [Bot], baragoon, Bing [Bot], sch and 99 guests