Zabbix Agent active checks problem

[lukaszor]

Hi. I have problem with proper communication between Agent and Server. Agent is installed on Windows2012server in different country than Zabbix_server.
Agent configuration is:

DebugLevel=3
#Passive check
Server=x.x.x.197
#Active check
ServerActive=x.x.x.197
hostname=monaco

On zabbix server i have created item with the hostname: monaco, and i have linked windows os template.

Now, on zabbix agent log i can see:

255928:20180614:121435.235 Starting Zabbix Agent [monaco]. Zabbix 3.4.6 (revision 76819).
255928:20180614:121435.235 **** Enabled features ****
255928:20180614:121435.235 IPv6 support: YES
255928:20180614:121435.235 TLS support: NO
255928:20180614:121435.235 **************************
255928:20180614:121435.235 using configuration file: c:\Zabbix\conf\zabbix_agentd.win.conf
255928:20180614:121435.235 agent #0 started [main process]
255660:20180614:121435.250 agent #1 started [collector]
256248:20180614:121435.250 agent #3 started[listener #2]
253604:20180614:121435.250 agent #2 started[listener #1]
256472:20180614:121435.250 agent #4 started[listener #3]
251544:20180614:121435.250 agent #5 started [active checks #1]
251544:20180614:121538.963 active check configuration update from [x.x.x.197:10051] started to fail (cannot connect to [[x.x.x.197]:10051]: (null))
251544:20180614:121638.757 active check configuration update from [x.x.x.197:10051] is working again

But Zabbix-server is not receiving any data from the agent... It displays the message saying : Get value from agent failed: cannot connect to [[x.x.x.2]:10051]: [4] Interrupted system call

I have checked on firewall on agent side and I can see outgoing traffic to Zabbixserver


How can I troubleshoot the problem?

[kloczek]

Test connectivity from the monitored host using telnet command "telnet x.x.x.2 1005"

[lukaszor]

I have tried telnet from agent computer to zabbix server as You said but i'm getting message "Connection closed by remote host". I have few agents running on local machines and they communicate ok with zabbix server, and i tried telnet locally and with the same result as remotly.

[kloczek]

I have tried telnet from agent computer to zabbix server as You said but i'm getting message "Connection closed by remote host". I have few agents running on local machines and they communicate ok with zabbix server, and i tried telnet locally and with the same result as remotly.

Zabbix server/proxy does not filter incoming connections because it does not check source address of the incoming connection.
Just try exactly the same command on the server/proxy to which you are trying to connect connecting to host IP or localhost.
If telnet command will show you established with output like below:

[tkloczko@domek tests]$ telnet 192.168.1.5 10051
Trying 192.168.1.5...
Connected to 192.168.1.5.
Escape character is '^]'.

and will show you something like:

[tkloczko@domek tests]$ telnet 92.242.132.16 10051
Trying 92.242.132.16...
telnet: connect to address 92.242.132.16: Connection refused

It will mean you are trying to connect to wrong address or something in the middle is filtering network traffic and/or even if you are using correct address (from agent perspective) something in the middle on network layer is translating this address.
You can check first by using "nmap -O <srv_or_prx.address>" (and comparing this output with the same command executed on the server/proxy host), and you can verify second by starting on listener side tcpdump and checking do you see network traffic which should come from agent side.

Nevertheless, as I wrote zabbix server or proxy does not filter incoming connections so it cannot cause "Connection refused" message which said that you see.
In other words I'm 100% sure that your problems are not related to the zabbix per se (if you are able to renet on 10051 to localhost on zabbix server/proxy host).

[nambiya]

I am too facing the issue : not able to connect to server from agent.

Error details just say NULL :

3896:20180627:075010.594 Starting Zabbix Agent [Windows host]. Zabbix 3.4.0 (revision 71462).
3896:20180627:075010.597 **** Enabled features ****
3896:20180627:075010.600 IPv6 support: YES
3896:20180627:075010.603 TLS support: NO
3896:20180627:075010.603 **************************
3896:20180627:075010.604 using configuration file: D:\zabbix\zabbix_agentd.conf
3896:20180627:075010.605 agent #0 started [main process]
3576:20180627:075010.605 agent #1 started [collector]
4280:20180627:075010.606 agent #2 started[listener #1]
772:20180627:075010.606 agent #5 started [active checks #1]
4340:20180627:075010.606 agent #6 started [active checks #2]
5808:20180627:075010.606 agent #4 started[listener #3]
2420:20180627:075010.607 agent #3 started[listener #2]
4340:20180627:075013.608 active check configuration update from [10.50.148.28:10051] started to fail (cannot connect to [[10.50.148.28]:10051]: (null)

[kernbug]

I am too facing the issue : not able to connect to server from agent.

4340:20180627:075013.608 active check configuration update from [10.50.148.28:10051] started to fail (cannot connect to [[10.50.148.28]:10051]: (null)

Hi,

Please show output from the Zabbix Server:

sudo iptables -L -x -v -n --line-numbers

[nambiya]

Please find below the output

Chain INPUT (policy ACCEPT 1601617 packets, 95787571 bytes)
num pkts bytes target prot opt in out source destination
1 9966 659735 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:10051
2 1 60 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:23
3 0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:10051
4 173241 10394460 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:10050

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
num pkts bytes target prot opt in out source destination

Chain OUTPUT (policy ACCEPT 1781373 packets, 108313087 bytes)
num pkts bytes target prot opt in out source destination

[kloczek]

If it is possible to use telnet to test connectivity and it works and zabbix active agent cannot connect to srv/prx most likely all what blocks here is SELinux and in such case all what is needed is add proper SELinux rules for zabbix or disable SELinux.