Zabbix is generating a lot of dns requests

[yarisken]

Hello,

I installed zabbix and everything is working fine.
I still have a problem with dns request. They are huge. For every request the zabbix agent does a dns lookup. I have read that this can be because in the .conf file i use zabbix.domainname instead of the ip. Can this help ? Zabbix is not using caching. If caching could be enabled this could also be a solution.

Another problem is ipv6 ( AAA ) request. On the servers ipv6 is disabled but the client still does dns request for ipv6. I have read that the agent is compiled with ipv6 support and if you want to disable this you have to recompile the agent. I used the agent from the epel repository. Is there another way ? Can i disabled ipv6 another way ?

Thx for your help.

Regards,

Jeroen

[BDiE8VNy]

To avoid name service lookups you have to configure ip addresses for host interfaces and select IP for connection.

It's up to the operating system to provide name service / host address caching.
I believe Windows does that out of the box. On Linux this is often done by nscd (namse service caching daemon) or more rarely be done by a local caching name server (e.g. via bind).

[yarisken]

It's exactly like you said. I have changed on my linux hosts to an ip-adres and now there is no problem anymore. Thx for your reply. Windows hosts do caching out-of-the-box.

[foobar]

I have the same problem.

With 50 hosts in Zabbix server, it sending about 16000(!) dns requests in a minute.

[yarisken]

Use only an ip on your servers to connect to the zabbix server. Change the interval of your items/triggers to a larger number.

[foobar]

I use IP in zabbix agents to connect to the Zabbix server.

Change the interval of your items/triggers to a larger number.

How interval of items connected with dns resolve of hosts? Is it resolve to IP in every check item?

[yarisken]

You have 2 things. A lot of traffic because of dns requests from the client to the zabbix server. In you case you use ip so that's ok. Then change the interval. Do you have many templates connected to 1 server ?

[foobar]

I cannot changed the interval It monitored critical metrics for me.

I have 1368 online items with different interval check.

I still do not understand how items connected with frequent dns resolves.

[tchjts1]

If you have Server= and ServerActive= in zabbix_agentd.conf using the IP address of your Zabbix server, it shouldn't be doing DNS queries.

Also, in the Zabbix GUI, for each host you should click on "IP" and not "DNS" for the "Connect using" configuration.

[foobar]

Also, in the Zabbix GUI, for each host you should click on "IP" and not "DNS" for the "Connect using" configuration.

It is not correct advice because if you have hundreds of hosts you do not have the ability to change IP for every host constantly.

[tchjts1]

It is not correct advice because if you have hundreds of hosts you do not have the ability to change IP for every host constantly.

Actually, it IS correct advice if you want to use IP instead of DNS. It is unfortunate that they do not have a way to do mass update for that particular setting through the GUI.

If you have the knowledge to do it through the API, all the more power to you.

And I don't know why you would have to do it "constantly". You change it once, and it is done.

[zalex_ua]

FYI - https://support.zabbix.com/browse/ZBXNEXT-1002

[ahahum]

AAAA Requests

I am seeing similar issue. I don't care about the DNS queries, but the problem I see is that if my host being queried is named server.domain.com, I see these queries to my DNS server on each attempt to check it:

AAAA server.domain.com
AAAA server.domain.com.domain.com (with DNS suffix added)
A server.domain.com

There are 2 extra requests and I can't seem to get Zabbix to stop requesting the IPv6 address first despite disabling it every way I can think of at the OS level.

A standard nslookup on the server queries only for IPv4.

I understand I can change it to check via IP address, but I'd like to be able to change IP addresses on servers without having to change it in multiple places.

Ideas?

[LenR]

Install a local caching dns server on you zabbix server and proxies, like bind-chroot. Best of both worlds, you configure with DNS, only new and ttl-expired searched leave the server.

[ahahum]

Install a local caching dns server on you zabbix server and proxies, like bind-chroot. Best of both worlds, you configure with DNS, only new and ttl-expired searched leave the server.

That's a good idea, and I may try it - is there no way to simply tell Zabbix agent to stop requesting IPv6 addresses?