Logical Devices Introduction

Logical devices enable you to plan your network fabric before selecting underlying hardware. By abstracting specific vendors and models you can design based on a common set of form factors like ports, speeds and roles. Some applications of logical devices include:

• Specifying speed and roles for specific ports (For example, the 48th port is always a leaf, or the speed of the 10th port is always 1 Gbps).
• Preparing for port speed transformations (For example, transforming one - 40 GbE port into four - 10 GbE ports).
• Using non-standard port speeds (For example, for a 1 GbE SFP in a 10 GbE port, the underlying hardware is automatically configured correctly.)
• Solving for automatic cable map generation that takes into account failure domains on modular systems (for example, a line card).

Logical devices include the following details:

Table 1: Logical Device Parameters

Name	Description
Logical device name	A unique name to identify the logical device, 64 characters or fewer
Panel	Port layout based on IP fabric, forwarding engine, line card (slot) or physical layout. A panel contains one or more port groups. A logical device includes one or more panels.
Port Group	A collection of ports with the same speed and role(s)
Number of ports	Number of ports in the port group
Speed	Speed of ports in the port group
Roles	Ports are configured to face the following types of devices: Superspine - used for superspines facing spines on 5-stage Clos data center fabric Spine - used for spines facing leafs, or for spines facing superspines on 5-stage Clos data center fabric Leaf - used for leafs facing spine or generic systems Access (Junos only) - Port is configured to face an access device. To learn more about this feature and its limitations, contact Juniper Support . Peer (link between two leaf devices) - used for MLAG domains to provide a trunk between two leaf switches Unused - configuration is not rendered and ports are not allocated (use to specify a dead port, for example) Generic - Certain roles are not specified in logical devices (for example, a firewall, external router, bare metal server, or load balancer).

From the left navigation menu, navigate to Design > Logical Devices to go to logical devices in the global catalog. Apstra ships with many predefined logical devices. Click a logical device name in the table to see its details. For our example, we'll use a logical device consisting of 7 ports with varying roles.

Logical devices are mapped to device profiles (specific vendor models) and they're used in rack types and rack-based templates.