Safeguard 13.9: Deploy Port-Level Access Control

Port-level access control closes a common gap between “we have network security” and “we control network attachment.” If an attacker, rogue device, or unmanaged asset can plug into an open switch port (or join a poorly governed SSID), they can often bypass perimeter assumptions and land directly inside trusted network segments. Safeguard 13.9 focuses your program on preventing that outcome by requiring controls at the point of connection: the port.

For a Compliance Officer, CCO, or GRC lead, the work is to convert this safeguard into: (1) a clearly scoped requirement (“which ports, which networks, which users/devices”), (2) an implemented technical standard (commonly 802.1X with a NAC/RADIUS backend), and (3) durable evidence that enforcement is active and exceptions are controlled. This page gives you requirement-level implementation guidance you can hand to network engineering and IT operations without losing the audit thread.

Primary sources for this safeguard are CIS Controls v8 and the CIS Controls Navigator v8, which provide the safeguard statement and framework context ¹.

Regulatory text

Framework requirement: “CIS Controls v8 safeguard 13.9 implementation expectation (Deploy Port-Level Access Control).” ¹

What the operator must do: Deploy technical controls on network access points (wired switch ports and, where applicable, wireless access) so only authorized users/devices can connect, and ensure the control operates consistently through configuration standards, monitoring, and evidence capture ¹.

Plain-English interpretation

• You are controlling network attachment. A device does not get network connectivity just because it can physically connect to a port or see an SSID.
• Authorization must be enforced by the network (for example, switch/WLAN authentication, dynamic VLAN assignment, quarantine VLANs), not left to honor-system procedures.
• “Deployed” includes operationalization: defined scope, consistent configuration, controlled exceptions, monitoring, and proof.

Who it applies to

Entity scope

Applies to enterprises and technology organizations implementing CIS Controls v8 ¹.

Operational scope (where you should apply it)

Prioritize areas where a device gaining connectivity creates outsized risk:

• Corporate offices, campuses, call centers, and branch sites with shared physical access.
• Data centers and wiring closets where ports may be patched or re-patched.
• High-trust networks (identity infrastructure, admin networks, sensitive application segments).
• Wireless networks that provide internal access (not just guest internet).

Typical owners

• Network Engineering (switching/WLAN, RADIUS/NAC)
• Identity and Access Management (certificates, device identity)
• Endpoint Engineering (supplicant configuration, MDM/EDR posture signals)
• GRC / Security Assurance (scope, exceptions, evidence, testing)

What you actually need to do (step-by-step)

Use this as an execution checklist that maps cleanly to audit evidence.

1) Define scope and control objective

1. Inventory enforcement points: managed switches, wireless controllers, and access layer networks where you can enforce authentication.
2. Classify ports/SSIDs by function: user access, VoIP, printer/IoT, building systems, lab, guest, uplinks/trunks.
3. Set a minimum control standard per class:
   • User access ports: authenticated access (target: 802.1X).
   • Non-user devices: certificate/MAB with strict MAC allowlisting only where justified.
   • Guest: isolated guest SSID/VLAN with no internal routing.

Deliverable: a one-page “Port-Level Access Control Standard” that states which control applies to which port types and networks, plus who can approve exceptions.

2) Choose enforcement approach (and document why)

Common patterns:

• 802.1X + RADIUS/NAC for primary enforcement (user/device auth).
• MAC Authentication Bypass (MAB) only for devices that cannot support 802.1X, with compensating controls (allowlist + restricted VLAN + monitoring).
• Dynamic VLAN / dACL assignment based on identity and posture.

Your documentation should state which mechanism is required by default and what qualifies for an exception. Tie this directly to the safeguard statement ¹.

3) Build the identity backbone

Port-level enforcement fails when identity is messy. Minimum build items:

• Authoritative identity sources: directory groups for users, device inventory for managed endpoints, certificate authority if using EAP-TLS.
• Device identity strategy: decide whether you authenticate by user, device, or both. Many environments use device certs for managed endpoints and a separate path for unmanaged.
• Certificate lifecycle controls: issuance, renewal, revocation, and ownership (especially if contractors and BYOD exist).

4) Implement configuration standards and templates

You need standard configs that engineers can stamp out at scale.

• Switch port templates for user access ports (802.1X enabled, fallback policy, unauthorized behavior).
• Standard VLANs (production, restricted, remediation/quarantine, guest).
• Wireless SSID standards (enterprise auth vs guest, segmentation, access controls).

GRC angle: request the “golden config” templates and change control records as evidence that this is standardized, not ad hoc.

5) Roll out in controlled phases

A practical rollout sequence that reduces outages:

• Monitor mode / low-impact mode first (where supported) to observe authentication outcomes.
• Expand to a pilot site or pilot user group.
• Broaden by port-class, then by site.

Operational requirement: define what “fail open” vs “fail closed” means for your environment, and document the decision with risk acceptance where needed.

6) Exception handling (make it tight and auditable)

You will have exceptions: legacy printers, lab gear, building systems, specialized appliances. Require:

• Business justification and device owner.
• Compensating controls (restricted VLAN, allowlisted destinations, additional monitoring).
• Expiration date and review cadence.
• Approval by a named authority (security/network plus business owner).

Keep a living “Port Access Exceptions Register” and reconcile it against NAC/switch policy periodically.

7) Monitoring, testing, and recurring evidence capture

Auditors ask two questions: “Is it configured?” and “Is it working?” Implement:

• Alerting on authentication failures, MAB events, and new/unknown MACs.
• Periodic tests: attempt to connect an unauthorized device to a controlled port, verify it lands in quarantine or is denied.
• Review reports: top ports with MAB usage, devices in restricted VLAN, bypass accounts, and policy changes.

If you use Daydream to operationalize CIS safeguards, map this safeguard to a control narrative and set recurring evidence tasks (for example: quarterly config snapshots, monthly exception register review, periodic NAC report exports). That “mapped + recurring” approach directly addresses the common gap of missing implementation evidence ¹.

Required evidence and artifacts to retain

Retain artifacts that prove design, implementation, and operation.

Governance and scope

• Port-Level Access Control Standard (scope, port classes, required methods, exception criteria)
• Network diagrams showing access layer scope and segmentation intent
• RACI or ownership matrix for NAC/RADIUS, switching, wireless, and exception approvals

Technical configuration evidence

• NAC/RADIUS policy exports (authentication methods, authorization rules, VLAN/dACL outcomes)
• Switch and wireless controller configuration snippets/templates showing enforcement enabled
• Change tickets or approvals for rollout phases and policy changes

Operational evidence

• Exception register with approvals, compensating controls, and expiry
• Monitoring reports (authentication failures, MAB usage, unauthorized device attempts)
• Test records (date, tester, method, outcome, remediation if failure)

Assessment-ready narratives

• A short control description mapped to Safeguard 13.9, including frequency of review and evidence list ¹

Common exam/audit questions and hangups

1. “Show me which ports are controlled.” Be ready with scope by site and port class, plus configurations or controller policies.
2. “How do you handle devices that can’t do 802.1X?” Auditors want strict exception logic, not “we allowlist everything.”
3. “How do you prevent bypass?” Expect scrutiny on shared credentials, static allowlists, and admin override processes.
4. “Prove it’s operating.” Provide recent reports/logs and a test record. Config alone rarely closes the loop.
5. “What about wireless?” If internal SSIDs exist, treat them as part of the same network-attachment control family.

Frequent implementation mistakes and how to avoid them

Mistake	Why it fails	How to avoid it
Treating 802.1X as “future roadmap” with no compensating control	Leaves open ports today	Define interim controls (disabled unused ports, restricted VLAN defaults) and track a rollout plan tied to scope
Overusing MAB	MACs are easy to spoof	Require documented justification, restricted VLAN, and monitoring for MAB endpoints
No exception expiry	Exceptions become permanent	Put expirations in the register and require re-approval
“Fail open” everywhere without risk sign-off	Turns enforcement into logging	Document where fail-open is allowed and capture risk acceptance for critical networks
Missing evidence cadence	You pass once, fail later	Set recurring evidence capture and reviews; Daydream can schedule and store artifacts against the safeguard 1

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this safeguard, so this page does not cite enforcement actions.

From a risk standpoint, weak port-level access control increases the likelihood that:

• Unmanaged or rogue devices gain internal access.
• Guests or contractors connect to internal segments unintentionally.
• Attackers bypass perimeter controls through physical access or misconfigured wireless.

Your best defense in an assessment is to show: controlled scope, technical enforcement, and repeatable evidence that the control works ¹.

A practical 30/60/90-day execution plan

First 30 days (Immediate)

• Define scope: sites, port types, SSIDs, and “must control” networks.
• Publish the Port-Level Access Control Standard and exception workflow.
• Pull current-state evidence: sample switch configs, WLAN settings, and any existing NAC policies.
• Stand up an exceptions register and start capturing approvals.

Next 60 days (Near-term)

• Pilot 802.1X (or equivalent) on a limited set of user access ports and one internal SSID (if applicable).
• Establish restricted/quarantine VLAN and routing rules.
• Implement monitoring and a repeatable report export process.
• Document and test a “new device connection” workflow (what happens, who responds, how it’s approved).

By 90 days (Operationalized)

• Expand enforcement across prioritized sites/segments.
• Reduce MAB footprint with a formal plan (device upgrades, certificate enablement, segmentation).
• Run a control effectiveness test and store results as evidence.
• Use Daydream to map Safeguard 13.9 to an owner, a control narrative, and recurring evidence tasks so your next assessment is a documentation exercise, not a scramble ¹.

Frequently Asked Questions

Does Safeguard 13.9 require 802.1X specifically?

CIS v8 states the requirement as “Deploy Port-Level Access Control,” so the requirement is outcome-based: enforce authorized network attachment ¹. 802.1X is a common way to meet it, but you should document your chosen mechanism and prove it operates.

What do we do with devices that cannot support 802.1X (printers, IoT, building systems)?

Treat them as exceptions with compensating controls: restricted VLANs, allowlisted destinations, and heightened monitoring. Keep an exception register with approvals and an expiry so exceptions do not become permanent.

Are guest networks in scope?

If guests can access internal resources, they are in scope because the control objective is preventing unauthorized internal attachment. If the guest network is isolated to internet-only, document that segmentation and keep configs as evidence.

What evidence is most persuasive to auditors?

A short control narrative mapped to the safeguard, NAC/RADIUS policy exports, representative switch/WLAN configs, an exceptions register, and a recent test record proving unauthorized devices are blocked or quarantined ¹.

Can we meet the requirement by disabling unused switch ports?

Disabling unused ports helps, but it does not fully address authorized access on active user ports. Use it as a baseline hardening control while you implement authenticated access on the ports that must remain enabled.

How do we keep this from becoming a one-time project?

Assign an owner, set a review cadence for policies and exceptions, and capture recurring evidence (policy exports, logs/reports, test results). Daydream can track the safeguard, schedule evidence collection, and keep artifacts ready for assessments ¹.

Footnotes

1. CIS Controls v8; CIS Controls Navigator v8