# Agent-based vs Agentless monitoring: A Comparison

[![Agent-based vs agentless monitoring in OpManager: Agent monitoring video](https://www.manageengine.com/network-monitoring/help/images/new-device-template-monitor.jpg)](https://www.youtube-nocookie.com/embed/MSmlyF_7m64)

[Agent-based](https://www.manageengine.com/network-monitoring/agent-based-monitoring.html) and [agentless monitoring](https://www.manageengine.com/network-monitoring/agentless-network-monitoring.html) are two types of server-based performance monitoring systems. While OpManager supports both monitoring methods, there is a key distinction between the two, which we'll discuss in detail.

- [Agent-based network monitoring](https://www.manageengine.com/network-monitoring/help/agent-based-vs-agentless-monitoring.html#agent)
  - [What is an agent?](https://www.manageengine.com/network-monitoring/help/agent-based-vs-agentless-monitoring.html#agent-1)
  - [Strengths](https://www.manageengine.com/network-monitoring/help/agent-based-vs-agentless-monitoring.html#agent-2)
  - [Shortcomings](https://www.manageengine.com/network-monitoring/help/agent-based-vs-agentless-monitoring.html#agent-3)
  - [When to go for Agent-based Monitoring?](https://www.manageengine.com/network-monitoring/help/agent-based-vs-agentless-monitoring.html#agent-4)
- [Agentless network monitoring](https://www.manageengine.com/network-monitoring/help/agent-based-vs-agentless-monitoring.html#agentless)
  - [Strengths](https://www.manageengine.com/network-monitoring/help/agent-based-vs-agentless-monitoring.html#agentless-1)
  - [Shortcomings](https://www.manageengine.com/network-monitoring/help/agent-based-vs-agentless-monitoring.html#agentless-2)
  - [When to go for agentless monitoring?](https://www.manageengine.com/network-monitoring/help/agent-based-vs-agentless-monitoring.html#agentless-3)

![Agent-based vs Agentless monitoring in OpManager: Architecture](https://www.manageengine.com/network-monitoring/help/images/agents-vs-agentless.jpg)

## Agent-based network monitoring?

As the name suggests, an agent-based network monitoring technique uses agents to monitor the devices in a network. The agents are installed on the devices that need to be monitored. These agents are in constant contact with the network monitoring tool and are involved in data collection. The collected data is then sent to the monitoring tool for tracking and management.

### What is an Agent?

An agent is a lightweight software application installed on end devices to monitor their performance. Agents collect monitoring data by themselves and send it to the main server for further tracking and analysis. The information flow is unidirectional, meaning only the agent can contact the main server, not the other way around.

Agents reduce the workload on the main server by collecting data independently. Furthermore, even when the OpManager server is down, no data is lost since the agent collects and stores data even if the primary server is under maintenance.

### Strengths

- Dependent protocols like WMI / CLI / SNMP / SSH / ICMP / Telnet (based remote communication) do not have to be enabled in the end system.
- A single outbound HTTPS connection from the end machine to the OpManager server eliminates the need for inbound connection requests to the end machine.
- Enabling only the necessary ports is sufficient rather than enabling all ports.
- Monitoring data is collected even when OpManager is down.
- Public exposure activities such as opening ports or allowing outside network requests are not required.
- This monitoring technique is more secure.
- ICMP or any other outbound connection is not required on the OpManager-installed server.

### Shortcomings

- An agent must be installed on all monitored servers.

### When to go for Agent-based Monitoring?

- When your credentials cannot be shared.
- When you cannot allow outside access requests to your network.
- When you cannot open your ports.
- Since WAN devices are movable and their IP addresses constantly change, this can be best handled using an agent-based monitoring technique.
- When your organization is a distributed enterprise.

## Agentless network monitoring

Agentless network monitoring monitors devices remotely using protocols, REST APIs, third parties, etc. [Agentless network monitoring](https://www.manageengine.com/network-monitoring/agentless-network-monitoring.html) does not require the installation of agents on network devices.

### Strengths

- Does not require the installation of agents.
- OpManager supports a wide range of monitor types for agentless monitoring.
- Supports virtual hosts.
- Supports all kinds of servers.

### Shortcomings

- Credentials must be shared.
- Dependent protocols like WMI / SNMP must be enabled in the end system.
- Dependent ports on the end machine and OpManager server must be enabled.
- When OpManager is down, monitoring data is not collected.

### When to go for agentless monitoring?

- Best suited for network devices such as servers, switches, routers, etc.
- When your network has virtual devices.
- When you do not want applications to be installed in your network.

The network world is not what it once was. Things are changing at an increasingly faster pace. Organizations are using networks that are becoming more complex day by day. Such complexity calls for both agent-based and agentless monitoring techniques.

Both techniques have their fair share of pros and cons. Hence, a network administrator must leverage the advantages and use techniques that are best suited for a given situation. Rather than focusing solely on which technique to use, a network administrator must focus on the end result and how to achieve it effectively.