Server can't communicate with client.

[jmangan]

I'm new to Zabbix so I have set up a small test network to get some experience. I have created two CentOS 7 vms running on a CentOS 7 host.

The server (Zabbix 3.4.15) is up and running and its local agent is communicating okay but my client will not make contact.

The two machines can ping each other and I can telnet from either to the other on TCP port 10050 using DNS name or IP. (I can also telnet from the client to the server on TCP port 10051).

On the server log the only error I can see is this one:
8170:20200412:091914.646 cannot send list of active checks to "192.168.144.246 ": host [Mail server] not found

From the searches I have done this generally appears to be a mismatch between the host name on the server and on the agent.

But if I run zabbix_agentd -t agent.hostname on the agent I get:
agent.hostname [s|Mail server]

which looks identical to me.

I have tried adding the host using either DNS name or IP address but it doesn't make any difference.

Any suggestions where I should look next?

Thanks.

[provels]

Does your configured hostname match (case,too) in the server and the client config? Maybe try "Mailserver" or "Mail_server" instead of "Mail server"? Did you add a namserver entry to your Zabbix server's net config? HTH

[jmangan]

I can try changing the name as you suggest but the Zabbix server name is Zabbix server and that works? I copied the server and client names above. They look identical to me.

As I said I’ve tried using both DNS name and IP address. Is there a parameter in the server config File for DNS servers rather than it using the system settings?

[provels]

The actual default hostname of the server is "zabbix". Try a hostname with no spaces.

appliance@zabbix:~$ hostname
zabbix
appliance@zabbix:~$

[jmangan]

No, that's not right. On the server:
[root@Zabbix ~]# zabbix_agentd -t agent.hostname
agent.hostname [s|Zabbix server]

As I understand it the machine host name is not the same as the agent hostname.

Also on the console:


Anyway, I deleted 'Mail server' from the console. Then I edited the mail server zabbix_agentd.conf and changed the hostname to Mailserver. I restarted the agent:
[root@mail zabbix]# zabbix_agentd -t agent.hostname
agent.hostname [s|Mailserver]

and then added the server back into the console using the IP address (so no DNS questions) but I get the same result but with the new name:
8170:20200413:135106.517 cannot send list of active checks to "192.168.144.246 ": host [Mailserver] not found

So the space isn't the issue.

[provels]

Make sure your zabbix_agentd.conf has:

Hostname=<is exactly the same as is defined on the server (case also)>
ServerActive=<z_server_ip>:10051
Server=<z_server_ip>
SourceIP=<windows_server_ip>
ListenIP=<windows_server_ip>
ListenPort=10050

[jmangan]

SourceIP=<windows_server_ip>
ListenIP=<windows_server_ip>

What windows server? This is all CentOS. I've duplicated the settings in the Zabbix server agent (which is working) on the mail server agent (apart from network IP rather than 127.0.0.1). I've checked case and spelling as you can see above. I've already tried calling the agent the hostname alone 'mail' and the FQDN 'mail.domain.name'. It doesn't make any difference.

[provels]

Sorry, I had pasted that out from another post I made helping another user with the agent on Windows. Maybe you could attach a copy of your Mailserver's zabbix_agentd.conf. Or just carry on.

[jmangan]

Well, I tried everything you said but it still makes no difference - except that it's not saying it can't find Mailserver in the zabbix server log at all now - but I've left it for two hours and it still isn't updating ro seeing an active agent.

There must be somewhere else to look to get a clue as to what the problem is?

agentd.conf
# This is a configuration file for Zabbix agent daemon (Unix)
# To get more information about Zabbix, visit http://www.zabbix.com

############ GENERAL PARAMETERS #################

### Option: PidFile
# Name of PID file.
#
# Mandatory: no
# Default:
# PidFile=/tmp/zabbix_agentd.pid

PidFile=/var/run/zabbix/zabbix_agentd.pid

### Option: LogType
# Specifies where log messages are written to:
# system - syslog
# file - file specified with LogFile parameter
# console - standard output
#
# Mandatory: no
# Default:
# LogType=file

### Option: LogFile
# Log file name for LogType 'file' parameter.
#
# Mandatory: no
# Default:
# LogFile=

LogFile=/var/log/zabbix/zabbix_agentd.log

### Option: LogFileSize
# Maximum size of log file in MB.
# 0 - disable automatic log rotation.
#
# Mandatory: no
# Range: 0-1024
# Default:
# LogFileSize=1

LogFileSize=0

### Option: DebugLevel
# Specifies debug level:
# 0 - basic information about starting and stopping of Zabbix processes
# 1 - critical information
# 2 - error information
# 3 - warnings
# 4 - for debugging (produces lots of information)
# 5 - extended debugging (produces even more information)
#
# Mandatory: no
# Range: 0-5
# Default:
# DebugLevel=3

### Option: SourceIP
# Source IP address for outgoing connections.
#
# Mandatory: no
# Default:
# SourceIP=
# Added value for SourceIP below - only IP interface on Mailserver
SourceIP=192.168.144.246

### Option: EnableRemoteCommands
# Whether remote commands from Zabbix server are allowed.
# 0 - not allowed
# 1 - allowed
#
# Mandatory: no
# Default:
# EnableRemoteCommands=0

### Option: LogRemoteCommands
# Enable logging of executed shell commands as warnings.
# 0 - disabled
# 1 - enabled
#
# Mandatory: no
# Default:
# LogRemoteCommands=0

##### Passive checks related

### Option: Server
# List of comma delimited IP addresses, optionally in CIDR notation, or hostnames of Zabbix servers and Zabbix proxies.
# Incoming connections will be accepted only from the hosts listed here.
# If IPv6 support is enabled then '127.0.0.1', '::127.0.0.1', '::ffff:127.0.0.1' are treated equally and '::/0' will allow any IPv4 or IPv6 address.
# '0.0.0.0/0' can be used to allow any IPv4 address.
# Example: Server=127.0.0.1,192.168.1.0/24,::1,2001:db8::/32,zabbix.domain
#
# Mandatory: yes, if StartAgents is not explicitly set to 0
# Default:
# Server=

# IP address added - Zabbix server
Server=192.168.144.244

### Option: ListenPort
# Agent will listen on this port for connections from the server.
#
# Mandatory: no
# Range: 1024-32767
# Default:
# Uncomment line below - evn though default
ListenPort=10050

### Option: ListenIP
# List of comma delimited IP addresses that the agent should listen on.
# First IP address is sent to Zabbix server if connecting to it to retrieve list of active checks.
#
# Mandatory: no
# Default:
# ListenIP=0.0.0.0
# Add ListenIP below event though only one available
ListenIP=192.168.144.246

### Option: StartAgents
# Number of pre-forked instances of zabbix_agentd that process passive checks.
# If set to 0, disables passive checks and the agent will not listen on any TCP port.
#
# Mandatory: no
# Range: 0-100
# Default:
# StartAgents=3

##### Active checks related

### Option: ServerActive
# List of comma delimited IPort (or hostnameort) pairs of Zabbix servers and Zabbix proxies for active checks.
# If port is not specified, default port is used.
# IPv6 addresses must be enclosed in square brackets if port for that host is specified.
# If port is not specified, square brackets for IPv6 addresses are optional.
# If this parameter is not specified, active checks are disabled.
# Example: ServerActive=127.0.0.1:20051,zabbix.domain,[::1]:30051,::1,[12fc::1]
#
# Mandatory: no
# Default:
# ServerActive=

# Zabbix Server IP address and port added
ServerActive=192.168.144.244:10051

### Option: Hostname
# Unique, case sensitive hostname.
# Required for active checks and must match hostname as configured on the server.
# Value is acquired from HostnameItem if undefined.
#
# Mandatory: no
# Default:
# Hostname=

# Local hostname
Hostname=Mailserver

### Option: HostnameItem
# Item used for generating Hostname if it is undefined. Ignored if Hostname is defined.
# Does not support UserParameters or aliases.
#
# Mandatory: no
# Default:
# HostnameItem=system.hostname

### Option: HostMetadata
# Optional parameter that defines host metadata.
# Host metadata is used at host auto-registration process.
# An agent will issue an error and not start if the value is over limit of 255 characters.
# If not defined, value will be acquired from HostMetadataItem.
#
# Mandatory: no
# Range: 0-255 characters
# Default:
# HostMetadata=

### Option: HostMetadataItem
# Optional parameter that defines an item used for getting host metadata.
# Host metadata is used at host auto-registration process.
# During an auto-registration request an agent will log a warning message if
# the value returned by specified item is over limit of 255 characters.
# This option is only used when HostMetadata is not defined.
#
# Mandatory: no
# Default:
# HostMetadataItem=

### Option: RefreshActiveChecks
# How often list of active checks is refreshed, in seconds.
#
# Mandatory: no
# Range: 60-3600
# Default:
# RefreshActiveChecks=120

### Option: BufferSend
# Do not keep data longer than N seconds in buffer.
#
# Mandatory: no
# Range: 1-3600
# Default:
# BufferSend=5

### Option: BufferSize
# Maximum number of values in a memory buffer. The agent will send
# all collected data to Zabbix Server or Proxy if the buffer is full.
#
# Mandatory: no
# Range: 2-65535
# Default:
# BufferSize=100

### Option: MaxLinesPerSecond
# Maximum number of new lines the agent will send per second to Zabbix Server
# or Proxy processing 'log' and 'logrt' active checks.
# The provided value will be overridden by the parameter 'maxlines',
# provided in 'log' or 'logrt' item keys.
#
# Mandatory: no
# Range: 1-1000
# Default:
# MaxLinesPerSecond=20

############ ADVANCED PARAMETERS #################

### Option: Alias
# Sets an alias for an item key. It can be used to substitute long and complex item key with a smaller and simpler one.
# Multiple Alias parameters may be present. Multiple parameters with the same Alias key are not allowed.
# Different Alias keys may reference the same item key.
# For example, to retrieve the ID of user 'zabbix':
# Alias=zabbix.userid:vfs.file.regexp[/etc/passwd,^zabbix:.[0-9]+),,,,\1]
# Now shorthand key zabbix.userid may be used to retrieve data.
# Aliases can be used in HostMetadataItem but not in HostnameItem parameters.
#
# Mandatory: no
# Range:
# Default:

### Option: Timeout
# Spend no more than Timeout seconds on processing
#
# Mandatory: no
# Range: 1-30
# Default:
# Timeout=3

### Option: AllowRoot
# Allow the agent to run as 'root'. If disabled and the agent is started by 'root', the agent
# will try to switch to the user specified by the User configuration option instead.
# Has no effect if started under a regular user.
# 0 - do not allow
# 1 - allow
#
# Mandatory: no
# Default:
# AllowRoot=0

### Option: User
# Drop privileges to a specific, existing user on the system.
# Only has effect if run as 'root' and AllowRoot is disabled.
#
# Mandatory: no
# Default:
# User=zabbix

### Option: Include
# You may include individual files or all files in a directory in the configuration file.
# Installing Zabbix will create include directory in /usr/local/etc, unless modified during the compile time.
#
# Mandatory: no
# Default:
# Include=

Include=/etc/zabbix/zabbix_agentd.d/*.conf

# Include=/usr/local/etc/zabbix_agentd.userparams.conf
# Include=/usr/local/etc/zabbix_agentd.conf.d/
# Include=/usr/local/etc/zabbix_agentd.conf.d/*.conf

####### USER-DEFINED MONITORED PARAMETERS #######

### Option: UnsafeUserParameters
# Allow all characters to be passed in arguments to user-defined parameters.
# The following characters are not allowed:
# \ ' " ` * ? [ ] { } ~ $ ! & ; ( ) < > | # @
# Additionally, newline characters are not allowed.
# 0 - do not allow
# 1 - allow
#
# Mandatory: no
# Range: 0-1
# Default:
# UnsafeUserParameters=0

### Option: UserParameter
# User-defined parameter to monitor. There can be several user-defined parameters.
# Format: UserParameter=<key>,<shell command>
# See 'zabbix_agentd' directory for examples.
#
# Mandatory: no
# Default:
# UserParameter=

####### LOADABLE MODULES #######

### Option: LoadModulePath
# Full path to location of agent modules.
# Default depends on compilation options.
#
# Mandatory: no
# Default:
# LoadModulePath=${libdir}/modules

### Option: LoadModule
# Module to load at agent startup. Modules are used to extend functionality of the agent.
# Format: LoadModule=<module.so>
# The modules must be located in directory specified by LoadModulePath.
# It is allowed to include multiple LoadModule parameters.
#
# Mandatory: no
# Default:
# LoadModule=

####### TLS-RELATED PARAMETERS #######

### Option: TLSConnect
# How the agent should connect to server or proxy. Used for active checks.
# Only one value can be specified:
# unencrypted - connect without encryption
# psk - connect using TLS and a pre-shared key
# cert - connect using TLS and a certificate
#
# Mandatory: yes, if TLS certificate or PSK parameters are defined (even for 'unencrypted' connection)
# Default:
# TLSConnect=unencrypted

### Option: TLSAccept
# What incoming connections to accept.
# Multiple values can be specified, separated by comma:
# unencrypted - accept connections without encryption
# psk - accept connections secured with TLS and a pre-shared key
# cert - accept connections secured with TLS and a certificate
#
# Mandatory: yes, if TLS certificate or PSK parameters are defined (even for 'unencrypted' connection)
# Default:
# TLSAccept=unencrypted

### Option: TLSCAFile
# Full pathname of a file containing the top-level CA(s) certificates for
# peer certificate verification.
#
# Mandatory: no
# Default:
# TLSCAFile=

### Option: TLSCRLFile
# Full pathname of a file containing revoked certificates.
#
# Mandatory: no
# Default:
# TLSCRLFile=

### Option: TLSServerCertIssuer
# Allowed server certificate issuer.
#
# Mandatory: no
# Default:
# TLSServerCertIssuer=

### Option: TLSServerCertSubject
# Allowed server certificate subject.
#
# Mandatory: no
# Default:
# TLSServerCertSubject=

### Option: TLSCertFile
# Full pathname of a file containing the agent certificate or certificate chain.
#
# Mandatory: no
# Default:
# TLSCertFile=

### Option: TLSKeyFile
# Full pathname of a file containing the agent private key.
#
# Mandatory: no
# Default:
# TLSKeyFile=

### Option: TLSPSKIdentity
# Unique, case sensitive string used to identify the pre-shared key.
#
# Mandatory: no
# Default:
# TLSPSKIdentity=

### Option: TLSPSKFile
# Full pathname of a file containing the pre-shared key.
#
# Mandatory: no
# Default:
# TLSPSKFile=


Thanks.

[provels]

You see the jobs running on both boxes and can ping by name and IP and telnet between them on 10050 and 10051? If no, maybe try a hosts file. No firewalls installed by default on these, right? That's about all I got.