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# InfiniBand Port GUID Discovery

Discovers InfiniBand port GUIDs from UFM and syncs them onto the matching Nautobot interfaces (`custom_fields.ib_guid`). GUIDs are written only onto compute-side interfaces; the selected switches anchor the topology and are never modified. Compute interfaces are resolved from Nautobot's cable topology, not from UFM node descriptions.

For step-by-step instructions, see the [InfiniBand Port GUID Discovery](/switch-infrastructure/config-manager/user-guides/infini-band-p-key-lifecycle/ib-port-guid-discovery) user guide.

The workflow is dry-run by default. A dry run computes the GUID-to-interface mappings without writing anything. Clear the Dry run option to apply them.

## User Interface

### Form Inputs

| Field              | Description                                                                                       | Required |
| :----------------- | :------------------------------------------------------------------------------------------------ | :------- |
| **Site**           | Site that scopes the device dropdowns                                                             | Yes      |
| **UFM Device**     | UFM appliance to read port GUIDs from. Lists devices with role `UFM` in the selected site.        | Yes      |
| **Switch Devices** | InfiniBand switches that anchor the topology; GUIDs land on the compute interfaces cabled to them | Yes      |
| **Dry run**        | Compute mappings without writing `ib_guid`. Enabled by default.                                   | No       |

![InfiniBand Port GUID Discovery workflow form](https://fdr-prod-docs-files-public.s3.us-east-1.amazonaws.com/config-manager.docs.buildwithfern.com/04168177d9e03ad66b338fc649a49d598c07a31e11f7b26f4ed217fd9256b525/_dot_dot_/assets/images/workflows/ibportguiddiscoveryworkflow-form.png?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6KXJSKKNFOCF7G4B%2F20260819%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20260819T015813Z&X-Amz-Expires=604800&X-Amz-Signature=dc42d8b4fe605bff268346af7d6c5c1824c3eb6392cc68a6a901b023ec558409&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)

## Workflow Execution

### Execution Stages

1. Resolve the UFM hostname and site from Nautobot
2. Fetch UFM ports and Nautobot cable topology, then compute GUID-to-compute-interface mappings (switch-owned ports and inter-switch links are dropped)
3. Sync `ib_guid` onto each resolved compute interface (skipped on dry run)