# Discovering devices using Layer2 maps

**How to draw Layer 2 maps?**

OpManager allows you to [discover Layer2 devices](https://www.manageengine.com/network-monitoring/how-to/discover-devices-lan-using-layer2.html) that are connected to your network and draws a [visual representation](https://www.manageengine.com/network-monitoring/network-visualization.html) of the same. This includes a detailed [map](https://www.manageengine.com/network-monitoring/network-mapping.html) of all the nodes, interconnected layers and port-to-port connectivity in addition to the interfaces.

To start discovering your layer2 devices, go to **Settings** > **Discovery** > **Layer2 Discovery**. This process can also be initiated from **Maps** > **Layer 2 Maps** > **Create New**.

Enter a name in the **Layer2 Map Name** section and proceed to type the IPv4 of your seed router in the **Router IPv4 Address** field.

**Configure a seed device :** A seed device is the core router or L3 switch in your network. The device must be SNMP-enabled so OpManager can query the device and draw the links automatically. The seed device should have "ipForwarding" set to 1 for the OID - .\1.3.6.1.2.1.4.1.0 and must have at least two or more interfaces (identified by querying the OID - \1.3.6.1.2.1.4.20.1.1).

The seed router will be connected to a vast number of devices. If you wish to restrict your Layer2 Map to a certain IP range, enter their Start IP and End IP and press the ‘+’ icon. You can specify multiple such entries to add more criteria.

**Discovery Mechanism:**  
OpManager supports multiple discovery protocols. Choose one (or more) that is implemented in your seed router/L3 switch. This will drastically reduce the time taken to discover the devices.

**Schedule interval:**  
As changes happen to the networks frequently, OpManager allows you to configure an interval (in days) to re-draw the map. For instance, if a change happens once in a week, you can configure OpManager to re-draw the map every seven days.

**Set Uplink Dependency:**  
This option helps in avoiding multiple device-down alerts when the parent device is down. Besides the layer2 discovery window, [Uplink Dependency](https://www.manageengine.com/network-monitoring/faq/device-dependency.html) can also be set from the Quick Configuration Wizard.

**Note:** Uplink Dependency happens only during **Device Import** and not during Layer2 Map discovery.

**Credentials:**  
Choose the SNMP credentials required for the seed router to identify the devices. You can add new credentials from the **Add Credentials** button.

![Device discovery using Layer2 maps in OpManager: Layer2 Discovery credentials](https://www.manageengine.com/network-monitoring/images/layer-2-discovery.jpg)

To learn how to customize your layer 2 Map, click [here](https://www.manageengine.com/network-monitoring/help/layer2-maps.html).