---
title: "NIST 800-171 3.13.5 (SC.L2-3.13.5): Public-Facing Subnets"
description: "NIST SP 800-171 3.13.5 Public-Facing Subnets: 5 SPRS points, not allowed on a CMMC POA&M. The text, what assessors check and the evidence."
url: https://policycortex.com/nist-800-171/system-and-communications-protection/3.13.5
sealed: 2026-11-11
amended: 2026-11-11
register: nist-800-171/system-and-communications-protection/3.13.5
records: 7
digest: sha3:69a678feb006920b1258dfec5b983aa47400a9649c2629d1e96baae0acf46ece
---

# NIST 800-171 3.13.5 (SC.L2-3.13.5): Public-Facing Subnets

NIST 800-171 / System and Communications Protection / 3.13.5

"Implement subnetworks for publicly accessible system components that are physically or logically separated from internal networks." ([NIST SP 800-171 Rev. 2, requirement 3.13.5](https://doi.org/10.6028/NIST.SP.800-171r2))

CMMC Level 2 practice SC.L2-3.13.5.

## What 3.13.5 means in practice

Anything the public can reach, such as a web server or a file transfer service, sits in its own subnetwork (often called a DMZ), physically or logically separated from internal networks, with rules that limit what can cross between them. In a cloud environment that usually means a separate subnet or virtual network for public endpoints, with rules that let only the needed traffic in.

## SPRS points and the CMMC POA&M

- **CMMC Level 2 practice**: SC.L2-3.13.5
- **SPRS points**: 5 points. When it is not met, the DoD Assessment Methodology subtracts 5 from the score of 110.
- **CMMC POA&M**: Not allowed. It is worth 5 points, and 32 CFR 170.21(a)(2)(ii) admits only requirements worth 1 point, with one exception: 3.13.11 when encryption is used but not FIPS validated.

Sources: [NIST SP 800-171 DoD Assessment Methodology, version 1.2.1 (June 24, 2020), Annex A](https://www.acq.osd.mil/asda/dpc/cp/cyber/docs/safeguarding/NIST-SP-800-171-Assessment-Methodology-Version-1.2.1-6.24.2020.pdf); [32 CFR 170.21, Plan of Action and Milestones requirements](https://www.ecfr.gov/current/title-32/section-170.21).

## What an assessor checks for 3.13.5

NIST SP 800-171A gives 2 determination statements for 3.13.5, each found satisfied or other than satisfied. Determine if:

- 3.13.5[a] publicly accessible system components are identified.
- 3.13.5[b] subnetworks for publicly accessible system components are physically or logically separated from internal networks.

[NIST SP 800-171A (June 2018), assessment objectives for 3.13.5](https://doi.org/10.6028/NIST.SP.800-171A)

## Evidence that shows 3.13.5 is met

- A list of publicly accessible system components.
- A network diagram showing the separate subnetwork that holds them.
- Firewall or network rules between that subnetwork and the internal networks.

## How PolicyCortex gathers the evidence

PolicyCortex reads this evidence with the collectors below, read only, and grades 3.13.5 from it. Each line says what the product checks.

- **Azure: Virtual networks.** Reads Azure virtual networks and checks that workloads are segmented into separate subnets.

## Related pages

- **Calculator**: [SPRS score calculator: mark 3.13.5 and the other 109 requirements and see the score.](https://policycortex.com/sprs-score-calculator#family-SC)
- **Sample package**: [Sample package: an SSP, a POA&M and an evidence chain the product generated from demonstration data.](https://policycortex.com/sample-package)
- **Family**: [All 16 System and Communications Protection requirements (3.13).](https://policycortex.com/nist-800-171/system-and-communications-protection)
- **Previous**: [3.13.4: Shared Resources](https://policycortex.com/nist-800-171/system-and-communications-protection/3.13.4)
- **Next**: [3.13.6: Deny by Default](https://policycortex.com/nist-800-171/system-and-communications-protection/3.13.6)
- **All requirements**: [All 110 NIST SP 800-171 requirements, by family.](https://policycortex.com/nist-800-171)

Meet the requirement once. Keep the evidence current. [Request Access](https://app.policycortex.com/auth?mode=request-access) · [Book a call](https://policycortex.com/book)

## Register colophon

| Seq | Label | SHA3-256 | Prev |
|---|---|---|---|
| REC 0000 | REQUIREMENT | 45d0f37033dd | 195f73e7d6fc |
| REC 0001 | MEANING | ddc988ca0dc3 | 45d0f37033dd |
| REC 0002 | POINTS AND POA&M | c0b520a08a00 | ddc988ca0dc3 |
| REC 0003 | ASSESSMENT OBJECTIVES | 1ff20d995a9a | c0b520a08a00 |
| REC 0004 | EVIDENCE | f57e36207a12 | 1ff20d995a9a |
| REC 0005 | COLLECTORS | da69396b5671 | f57e36207a12 |
| REC 0006 | RELATED | 69a678feb006 | da69396b5671 |

Head sha3:69a678feb006920b1258dfec5b983aa47400a9649c2629d1e96baae0acf46ece. Each digest is SHA3-256 over the previous digest, the register key, the record label, and the record copy; a second party can recompute it from this document.