Zabbix Agent to connecting to server.

[gregorywest]

I am running Zabbix 7.4.1 and am having issues conect remote computers. Oddly enough my switchs are connecting just fine under SNMP.
I have three devices with Zabbix Agents/SNMP
1) Zabbix server itself - works just fine
2) Linux box - both ZBX & SNMP indicators are black, yet I am getting CPU % information
3) Windows 10 - Box ZBX & SNMP are black, and getting no information on this device.

is there issue with the agent, and Zabbix 7.4.1?

[MRedbourne]

Are you using an active connection (Agent -> Server:10051) or a passive connection (Server -> Agent:10050)? Are the necessary ports open on any firewalls that may be in use? Is the agent listening? What happens if you port scan from one side to the other? If for example you have two devices:

Hostname	IP Address	Role
zabbix01.example.com	10.0.0.1	ZBX Server
fileserver.example.com	10.0.0.2	Windows File Server
ntp.example.com	10.0.0.3	Linux NTP Server

From Zabbix Server

• nmap -Pn -vvv -p 10050 10.0.0.2 10.0.0.3

From Client Devices

• nmap -Pn -vvv -p 10051 10.0.0.1

If those returned closed ports, you're missing firewall rules somewhere. Could be perimeter/internal firewalls (SonicWall, Palo Alto, etc.) or host-based firewalls (Windows Firewall, iptables, ufw, firewalld)

• (PowerShell) New-NetFirewallRule -DisplayName "Allow Zabbix Server to Agent" ` -Direction Inbound -LocalPort 10050 -Protocol TCP ` -RemoteAddress 10.0.0.0/8,172.16.0.0/12,192.168.0.0/16 ` -Action Allow
• sudo ufw allow from 10.0.0.0/8 to any port 10050 proto tcp
• sudo firewall-cmd --add-port=10050/tcp

Change your ports (or ranges) as you see fit. ChatGPT can help modify these commands if you want something more specific. Also, it wouldn't hurt to check your AppArmor or SELinux logs for linux.

[kz3]

Hey think that this is the issue
"is there issue with the agent, and Zabbix 7.4.1?"

Are you trying to use the zabbix agent on a windows 10 to catch data via snmp???

In windows 10 you need to add the snmp service via powershell or at least thats how it worked to me in windows server you can add the service on the server manager tool
the snmp service is no longer installed in windows 10 and you need to installe it manually

1º Install the snmp service
Powershell> Add-WindowsCapability -Online -Name SNMP.Client~~~~0.0.1.0

2º Create the file were the community name are going to be located
Powershell>New-Item -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\ Para meters\ValidCommunities" -Force | Out-Null

3º Add a community name , change the word public to your election
Powershell>New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\SNMP\ Para meters\ValidCommunities" -Name "public" -PropertyType DWord -Value 4 -Force

4º And then you need to create a firewall rule to allow inbound trafic on 161 via tcp and restart the snmp service , then it should work

[kz3]

to add the firewall rule
New-NetFirewallRule -DisplayName "SNMP" -Protocol UDP -LocalPort 161 -Action Allow -Direction Inbound
And to restart the snmp service
Restart-Service -Name SNMP -Force

Once restarted i will try to snmpwalk from terminal
because is faster than waiting the device to add on the UI

try
snmpwalk -v 2c -c yourcommunityname ipfromthewindows10

[gregorywest]

I did nmap from Zabbix server to the two workstations. On both port 10050 was open, 10051 closed. From workstation to server both 10050 and 10051 are closed. Did not think I had a firewall running on the server. Everything is behind a fairly massive firewall facing the internet. Server ports open are 22, 80, 10000. I checked all processes on the Zabbix server. There is no firewall running. Could I be missing something in one of the .CONF files?

re: SNMP this is a separate issue, I have SNMP configured on the workstation, but I will double check it. I did run nmap from the server to the windows workstation port 161 is showing as being closed.

Greg

P.S.
Here is nmap from the zabbix server itself:
root@Zibbix:/etc/zabbix# nmap -Pn -vvv -p 10050 10.10.10.71
Starting Nmap 7.93 ( https://nmap.org ) at 2025-08-25 10:47 CDT
Initiating Parallel DNS resolution of 1 host. at 10:47
Completed Parallel DNS resolution of 1 host. at 10:47, 0.01s elapsed
DNS resolution of 1 IPs took 0.01s. Mode: Async [#: 2, OK: 0, NX: 1, DR: 0, SF: 0, TR: 1, CN: 0]
Initiating SYN Stealth Scan at 10:47
Scanning 10.10.10.71 [1 port]
Discovered open port 10050/tcp on 10.10.10.71
Completed SYN Stealth Scan at 10:47, 0.03s elapsed (1 total ports)
Nmap scan report for 10.10.10.71
Host is up, received user-set (0.00023s latency).
Scanned at 2025-08-25 10:47:28 CDT for 0s

PORT STATE SERVICE REASON
10050/tcp open zabbix-agent syn-ack ttl 64

Read data files from: /usr/bin/../share/nmap
Nmap done: 1 IP address (1 host up) scanned in 0.47 seconds
Raw packets sent: 1 (44B) | Rcvd: 2 (88B)
root@Zibbix:/etc/zabbix#
root@Zibbix:/etc/zabbix# nmap -Pn -vvv -p 10051 10.10.10.71
Starting Nmap 7.93 ( https://nmap.org ) at 2025-08-25 10:50 CDT
Initiating Parallel DNS resolution of 1 host. at 10:50
Completed Parallel DNS resolution of 1 host. at 10:50, 0.01s elapsed
DNS resolution of 1 IPs took 0.01s. Mode: Async [#: 2, OK: 0, NX: 1, DR: 0, SF: 0, TR: 1, CN: 0]
Initiating SYN Stealth Scan at 10:50
Scanning 10.10.10.71 [1 port]
Discovered open port 10051/tcp on 10.10.10.71
Completed SYN Stealth Scan at 10:50, 0.03s elapsed (1 total ports)
Nmap scan report for 10.10.10.71
Host is up, received user-set (0.00025s latency).
Scanned at 2025-08-25 10:50:08 CDT for 0s

PORT STATE SERVICE REASON
10051/tcp open zabbix-trapper syn-ack ttl 64

Read data files from: /usr/bin/../share/nmap
Nmap done: 1 IP address (1 host up) scanned in 0.47 seconds
Raw packets sent: 1 (44B) | Rcvd: 2 (88B)
root@Zibbix:/etc/zabbix#

I have verified there is no firewall running. Is there something in the agent that would stop it from listening to the server if configured wrong?

[kz3]

Heyy
So as i understand now the problem is whit the conection from the zabbix server to a workstation via zabbix agent on 10050

the connection attemps are over a windows or linux ????
just asking just to say that in linux the minimum for the agent on the host to work is at least in my case(ubuntu 24.04) the minimun config required in the /etc/zabbix/zabbix-agent.conf is
SERVER=<yourserverip>
ListenPort=<yourlistenport>

On windows is faster that just executing the .exe agent downloaded from https://www.zabbix.com/la/download_agents
you just have yo put the server ip

by knowing that you already have switches and other host even via snmp it means that zabbix is working good
it is strange for me that it isn´t working because the 10050

is the agent running???
because sometimes by changing something on the .CONF on the agents they fail

try to conect from the zabbix server and then watch the logs of the agents

[gregorywest]

Server is Linux, WS one windows, one Linux. Let me verify the .CONF. And yes the windows agent is running. been tripped by agents not running in the past

[kz3]

This works for both windows and linux
Server=theipfromtheserver
ListenPort=usually10050
ListenIP=iusuallyleaveitlikethat

[gregorywest]

I had the ListenIP #'d out. Set it to what you have. Here is an odd thing. I have a zabbix_agent2.conf, but not a zabbix-agent2.conf _ vs - Which is correct?

Here is the odd part. With Windows WS is found with the agent discovery:
it is Master-New 10.10.10.216. But on the Hosts screen showing unavailable.

[kz3]

In windows the conf appears like zabbix_agentd.conf
so its good

yesterday you said " Everything is behind a fairly massive firewall facing the internet. Server ports open are 22, 80, 10000"

maybe it was a typo but the only idea i have at this moment is that really the port 10000 was open instead of 10050
because on the same range of ips you have connection to hosts via snmp

i just checked an windows server but except the snmp everithing related to te agents are the same

What i checked was this

1º a network rule


2º The agent conf - its even working just whit the server ip so my bad



3º Agent is running



4º trying a zabbix get from the zabbix server

zabbix_get -s 192.168.184.126 -p 10050 -k "agent.ping"




This is just working . maybe take a look in what i quoted before about the firewall and the port open 10000 instead of 10050
The 99,99% of problems ive had whit connections at the end most of them were closed ports and firewalls

i hope it helps till tomorrow

[gregorywest]

zabbix_get -s 192.168.184.126 -p 10050 -k "agent.ping" returned a 1
10000 is WEBMIN (Web browser server admin program. It is expected. The firewall is between the 10.10.8.1/22 network and the internet propper. There should be nothing between the devices on the 10.10...... backbone.

Very odd (or not) I have three Android tablets/phones using the "Unofficial Zabbix Agent" and they are showing up (yellow ZBX icons.

Looking more and more like a WS issue, not a server issue.
Now this is interesting. From the Linux WS nmap - 10051 shows up. Might be a different issue on the linux WS. Will look into that now.
pi@PiTorrent:~ $ nmap -Pn -vvv -p 10051 10.10.10.71
Starting Nmap 7.70 ( https://nmap.org ) at 2025-08-26 09:24 CDT
Initiating Parallel DNS resolution of 1 host. at 09:24
Completed Parallel DNS resolution of 1 host. at 09:24, 0.03s elapsed
DNS resolution of 1 IPs took 0.03s. Mode: Async [#: 4, OK: 0, NX: 1, DR: 0, SF: 0, TR: 1, CN: 0]
Initiating Connect Scan at 09:24
Scanning 10.10.10.71 [1 port]
Discovered open port 10051/tcp on 10.10.10.71
Completed Connect Scan at 09:24, 0.01s elapsed (1 total ports)
Nmap scan report for 10.10.10.71
Host is up, received user-set (0.0056s latency).
Scanned at 2025-08-26 09:24:48 CDT for 1s

PORT STATE SERVICE REASON
10051/tcp open zabbix-trapper syn-ack

Read data files from: /usr/bin/../share/nmap
Nmap done: 1 IP address (1 host up) scanned in 0.17 seconds
pi@PiTorrent:~ $

[gregorywest]

I checked the windows firewall settings. As expected the firewall appears to be off.

On odd thing, I am getting data from my PI's but the ZBX indicator is off:

Is this normal?
Greg

So Linux sort of working, windows not working...... god I hate windows!

[gregorywest]

OK got everything connected and talking. Switched all the problem workstations from "Agent Active" to "Agent". What is the difference between Active and 'regular'
Greg

[troffasky]

Active = agent connects in to server and delivers metrics. Hostnames must be unique. The items also are of their own type.
Passive = server connects to agent and polls metrics. Hostnames are not important.