Connection issues with Zabbix agent/Proxies on Nginx reverse proxy

[fred1984]

Dear guys,

I hope this post is not a duplicate on another and I'm sorry if it is, but so far i didn't found anywhere the same problem. Also I normally diagnosed the cause but I don't know how to resolve it or if it is possible to resolve ( spent few days already on it...)


so here is the situation:

-we are testing zabbix (v6) server on a cloud server with currently assigned a public IP (under Ubuntu 20.04).
- our company is using a nginx reverse proxy on another cloud server which has, as well, another public IP (under windows 2016)
- I successfully reverse proxy zabbix server (followed the instructions from the official youtube video: https://www.youtube.com/watch?v=UjYZRm0ss30) and i customized a little bit to match to my situation

server {
listen 443 ssl;
server_name zabbix.server.com;

location / {

proxy_pass http://PublicIPZabbixServer:80$request_uri;

proxy_http_version 1.1;

}

}

but i have a problem with the agents (tested in active mode and without encryption at that time). I certainly missed some skills , but my objective is to proxy also the agent into my main nginx server and only communicate with this nginx server. when i setup the Zabbix agents with my nginx server name (zabbix.server.com) agent refuse to connect and logs show a header issue:

2148:20220317:113215.266 Starting Zabbix Agent [AgentHostname]. Zabbix 6.0.2 (revision d726a4d916).
2148:20220317:113215.271 **** Enabled features ****
2148:20220317:113215.276 IPv6 support: YES
2148:20220317:113215.281 TLS support: NO
2148:20220317:113215.285 **************************
2148:20220317:113215.289 using configuration file: c:\Program Files\Zabbix6.0.2\conf\zabbix_agentd.conf
2148:20220317:113215.874 agent #0 started [main process]
4032:20220317:113215.880 agent #1 started [collector]
8464:20220317:113215.885 agent #3 started[listener #2]
10256:20220317:113215.890 agent #5 started [active checks #1]
13256:20220317:113215.895 agent #4 started[listener #3]
8404:20220317:113215.901 agent #2 started[listener #1]
10256:20220317:113215.987 Message from zabbix.server.com is missing header. Message ignored.
10256:20220317:113215.998 Unable to receive from [zabbix.server.com]:10051 []
10256:20220317:113216.009 Active check configuration update started to fail

I tried to add different header commands found from the forum : https://www.zabbix.com/forum/zabbix-...oxy-with-nginx but it seems there is not changes

I also added into the reverse proxy an entry for the port 10051 just in case:

server {

listen 10051;

#server_name zabbix.server.com;
location / {

proxy_pass http://PublicIPZabbixServer:10051$request_uri;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_http_version 1.1;

}

}

I'm pretty sure something is incorrect on my nginx proxy instruction but i don't know what.

The reason of this, is later on, the Zabbix server will not have a public IP, and it will be connected with internal IP with the Nginx server. So all connections must go through my Nginx server.

That's it, i don't know if I'm clear, ask me question if it is, and i hope this post can find a solution

Thanks in Advance,
Frederic

[Atsushi]

Communication between Zabbix server and Zabbix agent uses its own protocol instead of HTTP or HTTPS, so maybe you need to use stream?

https://docs.nginx.com/nginx/admin-guide/load-balancer/tcp-udp-load-balancer/

[fred1984]

Hi Atsushi,

Thank you , indeed the problem comes from here! And indeed the Agent is not using HTTP protocol, so i didn't realized this problem

For information for other people with this problem just add this:

1 Add the HTML GUI reverse proxy
2 Below the HTML tag, create a new one stream:

stream {

upstream zabbixagent {

server PublicIPZabbixServer:10051;

}
server {

listen 10051;
proxy_pass zabbixagent;

}

}

Thanks again !