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Logical Devices (Datacenter Design)

Logical Device Overview

Logical devices are abstractions of physical devices that specify common device form factors such as number, speed and roles of ports. Vendor-specific information is not included, which lets you plan your network before selecting vendors and hardware device models. (After selecting hardware devices, logical devices are associated with physical devices with interface maps.) Logical devices are used in rack types and rack-based templates. 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.
Port Group A group 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:
  • Superspines (5-stage DC fabric only)
  • Spine
  • Leaf
  • Access (limited support) - 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)
  • Unused - not rendered (for example, a dead port)
  • 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. Click a logical device name to see its details. You can create, clone, edit, and delete logical devices.

Create Logical Device

  1. From the left navigation menu, navigate to Design > Logical Devices and click Create Logical Device.
  2. Enter a unique logical device name.
  3. The default panel layout consists of 24 ports (2 rows of 12 ports each). For a different layout, select the number and arrangement of ports to match your requirements by dragging from the bottom-right corner of the layout.
  4. Select the ports for the port group by dragging to select contiguous ports, or by clicking individual ports. Clicking a port again deselects it.
  5. Select port speed, and applicable role(s) for the selected ports.
  6. Click Create Port Group (bottom-middle) to create the port group.
  7. If unassigned ports remain, repeat the previous two steps until all ports are assigned. For any ports that will not be used, assign them the Unused role.
  8. To add a panel, click Add Panel (bottom-middle) and repeat the steps as for the first panel.
  9. Click Create (bottom-right) to create the logical device and return to the table view.

Example: Create Logical Device

Let's create a logical device with one panel containing one port group with 96 - 10 GbE ports and a second panel containing one port group with 8 - 40 GbE ports.

  1. From the left navigation menu, navigate to Design > Logical Devices and click Create Logical Device.
  2. A descriptive name is helpful when referring to the logical device later. For our example we entered 96x10-8x40-2, which represents the following characteristics:
    • 96x10 - one panel with 96 - 10 GbE ports
    • 8x40 - one panel with 8 - 40 GbE ports
    • 2 - number of panels (rack units)
  3. For the port group in the first panel, drag the bottom-right corner of the port layout to change the default 2x12 configuration to a 3x32 configuration. Leave the number of ports (96) and speed (10 Gbps) as is, and select the Generic port role (Connected to).
  4. Click Create Port Group (bottom-middle), then click Add Panel (bottom-middle).
  5. Drag the bottom-right corner of the port layout to change the configuration to 2x4. Leave the number or ports (8) as is, change the speed to 40 Gbps, and connect them to Superspine, Spine, and Generic.
  6. Click Create Port Group, then click Create (bottom-right). The new logical device appears in the table view. (In the overview above, it's the first one in the table.)

Edit Logical Device

If a logical device is linked to an interface map, it cannot be changed. When you change a logical device in the global catalog, rack types and templates that previously embedded that logical device are not affected. This prevents potentially unintended changes to existing rack types and templates. If your intent is for a rack type or template to use a modified logical device, then you must re-import the rack type into the template.
  1. Either from the table view (Design > Logical Device) or the details view, click the Edit button for the logical device to edit.
  2. Make your changes.
    • To change port group details, access the dialog by clicking its description.
    • To add or remove ports from a port group, drag from the bottom-right corner of the port group layout to resize it. If you added ports, enter port speed and role(s).
    • To remove a port group, click the delete button (upper-right).
    • To add a panel, click Add Panel and enter relevant port group details.
  3. Click Update (bottom-right) to update the logical device in the global catalog and return to the table view.

Delete Logical Device

If a logical device is linked to an interface map, it cannot be deleted.
  1. Either from the table view (Design > Logical Devices) or the details view, click the Delete button for the logical device to delete.
  2. Click Delete Logical Device to delete the logical device from the global catalog and return to the table view.