Table of Contents
2 Active agent autoregistration
Overview
It is possible to allow active Zabbix agent autoregistration, after which the server can start monitoring them. This way new hosts can be added for monitoring without configuring them manually on the server.
Autoregistration can happen when a previously unknown active agent asks for checks.
The feature might be very handy for automatic monitoring of new Cloud nodes. As soon as you have a new node in the Cloud Zabbix will automatically start the collection of performance and availability data of the host.
Active agent autoregistration also supports the monitoring of added hosts with passive checks. When the active agent asks for checks, providing it has the 'ListenIP' or 'ListenPort' configuration parameters defined in the configuration file, these are sent along to the server. (If multiple IP addresses are specified, the first one is sent to the server.)
Server, when adding the new autoregistered host, uses the received IP address and port to configure the agent. If no IP address value is received, the one used for the incoming connection is used. If no port value is received, 10050 is used.
It is possible to specify that the host should be autoregistered with a DNS name as the default agent interface.
Autoregistration is rerun:
- if host metadata information changes:
- due to HostMetadata changed and agent restarted
- due to value returned by HostMetadataItem changed
- for manually created hosts with metadata missing
- if a host is manually changed to be monitored by another Zabbix proxy
- if autoregistration for the same host comes from a new Zabbix proxy
The active agent autoregistration heartbeat for Zabbix server and Zabbix proxy is 120 seconds. So in case a discovered host is deleted, the autoregistration will be rerun in 120 seconds.
Configuration
Specify server
Make sure you have the Zabbix server identified in the agent configuration file - zabbix_agentd.conf
Unless you specifically define a Hostname in zabbix_agentd.conf, the system hostname of agent location will be used by server for naming the host. The system hostname in Linux can be obtained by running the 'hostname' command.
If Hostname is defined in Zabbix agent configuration as a comma-delimited list of hosts, hosts will be created for all listed hostnames.
Restart the agent after making any changes to the configuration file.
Action for active agent autoregistration
When server receives an autoregistration request from an agent it calls an action. An action of event source "Autoregistration" must be configured for agent autoregistration.
Setting up network discovery is not required to have active agents autoregister.
In the Zabbix frontend, go to Alerts → Actions, select Autoregistration actions and click on Create action:
- In the Action tab, give your action a name
- Optionally specify conditions. You can do a substring match or regular expression match in the conditions for host name/host metadata. If you are going to use the "Host metadata" condition, see the next section.
- In the Operations tab, add relevant operations, such as - 'Add host', 'Add to host group' (for example, Discovered hosts), 'Link templates', etc.
If the hosts that will be autoregistering are likely to be supported for active monitoring only (such as hosts that are firewalled from your Zabbix server) then you might want to create a specific template like Template_Linux-active to link to.
Created hosts are added to the Discovered hosts group (by default, configurable in Administration → General → Other). If you wish hosts to be added to another group, add a Remove from host group operation (specifying "Discovered hosts") and also add an Add to host group operation (specifying another host group), because a host must belong to a host group.
Secure autoregistration
A secure way of autoregistration is possible by configuring PSK-based authentication with encrypted connections.
The level of encryption is configured globally in Administration → General → Autoregistration. It is possible to select no encryption, TLS encryption with PSK authentication or both (so that some hosts may register without encryption while others through encryption).
Authentication by PSK is verified by Zabbix server before adding a host. If successful, the host is added and Connections from/to host are set to 'PSK' only with identity/pre-shared key the same as in the global autoregistration setting.
To ensure security of autoregistration on installations using proxies, encryption between Zabbix server and proxy should be enabled.
Using DNS as default interface
HostInterface and HostInterfaceItem configuration parameters allow to specify a custom value for the host interface during autoregistration.
More specifically, they are useful if the host should be autoregistered with a DNS name as the default agent interface rather than its IP address. In that case the DNS name should be specified or returned as the value of either HostInterface or HostInterfaceItem parameters. Note that if the value of one of the two parameters changes, the autoregistered host interface is updated. So it is possible to update the default interface to another DNS name or update it to an IP address. For the changes to take effect though, the agent has to be restarted.
If HostInterface or HostInterfaceItem parameters are not configured, the listen_dns parameter is resolved from the IP address. If such resolving is configured incorrectly, it may break autoregistration because of invalid hostname.
Using host metadata
When agent is sending an autoregistration request to the server it sends its hostname. In some cases (for example, Amazon cloud nodes) a hostname is not enough for Zabbix server to differentiate discovered hosts. Host metadata can be optionally used to send other information from an agent to the server.
Host metadata is configured in the agent configuration file - zabbix_agentd.conf. There are 2 ways of specifying host metadata in the configuration file:
See the description of the options in the link above.
The HostMetadataItem parameter may return up to 65535 UTF-8 code points. A longer value will be truncated.
Note that on MySQL, the effective maximum length in characters will be less if the returned value contains multibyte characters. For example, a value containing 3-byte characters only will be limited to 21844 characters in total, while a value containing 4-byte characters only will be limited to 16383 symbols.
An autoregistration attempt happens every time an active agent sends a request to refresh active checks to the server. The delay between requests is specified in the RefreshActiveChecks parameter of the agent. The first request is sent immediately after the agent is restarted.
Example 1
Using host metadata to distinguish between Linux and Windows hosts.
Say you would like the hosts to be autoregistered by the Zabbix server. You have active Zabbix agents (see "Configuration" section above) on your network. There are Windows hosts and Linux hosts on your network and you have "Linux by Zabbix agent" and "Windows by Zabbix agent" templates available in your Zabbix frontend. So at host registration, you would like the appropriate Linux/Windows template to be applied to the host being registered. By default, only the hostname is sent to the server at autoregistration, which might not be enough. In order to make sure the proper template is applied to the host you should use host metadata.
Frontend configuration
The first thing to do is to configure the frontend. Create 2 actions. The first action:
- Name: Linux host autoregistration
- Conditions: Host metadata contains Linux
- Operations: Link templates: Linux
You can skip an "Add host" operation in this case. Linking a template to a host requires adding the host first so the server will do that automatically.
The second action:
- Name: Windows host autoregistration
- Conditions: Host metadata contains Windows
- Operations: Link templates: Windows
Agent configuration
Now you need to configure the agents. Add the next line to the agent configuration files:
This way you make sure host metadata will contain "Linux" or "Windows" depending on the host an agent is running on. An example of host metadata in this case:
Linux: Linux server3 3.2.0-4-686-pae #1 SMP Debian 3.2.41-2 i686 GNU/Linux
Windows: Windows WIN-0PXGGSTYNHO 6.0.6001 Windows Server 2008 Service Pack 1 Intel IA-32Do not forget to restart the agent after making any changes to the configuration file.
Example 2
Step 1
Using host metadata to allow some basic protection against unwanted hosts registering.
Frontend configuration
Create an action in the frontend, using some hard-to-guess secret code to disallow unwanted hosts:
- Name: Autoregistration action Linux
- Conditions:
- Type of calculation: AND
- Condition (A): Host metadata contains //Linux//
- Condition (B): Host metadata contains //21df83bf21bf0be663090bb8d4128558ab9b95fba66a6dbf834f8b91ae5e08ae//
- Operations:
- Send message to users: Admin via all media
- Add to host groups: Linux servers
- Link templates: Linux
Please note that this method alone does not provide strong protection because data is transmitted in plain text. Configuration cache reload is required for changes to have an immediate effect.
Agent configuration
Add the next line to the agent configuration file:
where "Linux" is a platform, and the rest of the string is the hard-to-guess secret text.
Do not forget to restart the agent after making any changes to the configuration file.
Step 2
It is possible to add additional monitoring for an already registered host.
Frontend configuration
Update the action in the frontend:
- Name: Autoregistration action Linux
- Conditions:
- Type of calculation: AND
- Condition (A): Host metadata contains Linux
- Condition (B): Host metadata contains 21df83bf21bf0be663090bb8d4128558ab9b95fba66a6dbf834f8b91ae5e08ae
- Operations:
- Send message to users: Admin via all media
- Add to host groups: Linux servers
- Link templates: Linux
- Link templates: MySQL by Zabbix Agent
Agent configuration
Update the next line in the agent configuration file:
Do not forget to restart the agent after making any changes to the configuration file.