Mirror every monitored domain controller to a standalone identity sensor

Keep this document to one review outcome: Mirror every monitored domain controller to a standalone identity sensor. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official Configure port mirroring from Microsoft supports the following bounded statements:

• A standalone sensor needs port mirroring or a network TAP to see domain-controller network traffic. The research record locates this support at Opening overview.
• Microsoft directs organizations using port mirroring to configure each monitored domain controller as a traffic source and coordinate with networking or virtualization teams. The research record locates this support at Port-mirroring scope paragraph.

These statements are the factual basis for this document. Do not extend them into a broader assurance. Review Defender for Identity workspaces, sensors, directory-service accounts, action accounts, network paths, roles, and deployment health only where the source and recorded environment align.

What the source does not establish

Mirrored traffic does not supply the ETW coverage unavailable to standalone sensors, and switch-specific configuration remains vendor dependent. No current deployment state or change approval follows from the source alone. Validate Active Directory, Windows DNS, time, certificates, domain-controller resources, network capture, cloud connectivity, and security operations, and treat examples or options as conditional inputs rather than defaults.

Applicability questions

• For source statement 1 at Opening overview, which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Port-mirroring scope paragraph, which observable configuration, record, or test can confirm applicability here?
• Which deployed instance of Defender for Identity workspaces, sensors, directory-service accounts, action accounts, network paths, roles, and deployment health will be compared with the source, and why that instance?
• How will the review distinguish a source mismatch from a failure in Active Directory, Windows DNS, time, certificates, domain-controller resources, network capture, cloud connectivity, and security operations?
• Who approves the conclusion, exception, test window, and rollback threshold?

DSE recommendation:

DSE recommends using the cited source as the evidence anchor for this decision. Start with applicability, then compare the observed state with the cited source. Record the source location, examined part of Defender for Identity workspaces, sensors, directory-service accounts, action accounts, network paths, roles, and deployment health, observed and expected states, owner, and reason for deviation.

For an approved change, define prerequisites, a limited test path, success and stop conditions, monitoring, and rollback. Check Active Directory, Windows DNS, time, certificates, domain-controller resources, network capture, cloud connectivity, and security operations in design order. Protect credentials, keys, recovery material, personal data, and sensitive topology in evidence.

Verification and evidence

Keep the source locations Opening overview; Port-mirroring scope paragraph adjacent to the sanitized artifacts used for comparison. Prefer sensor inventory, service and action-account permissions, health alerts, connectivity tests, portal state, and controlled detection tests, with enough identity and timing data for an independent recheck.

Preserve both successful and failed observations, along with approval and rollback evidence. Avoid uncontrolled production experiments. Assign an expiry or event-driven recheck so the conclusion is not treated as permanent.

Official references

• Configure port mirroring — Microsoft