CMMC Level 1 · System & Communications Protection

CMMC Level 1 SC.L1-b.1.xi: Subnetwork Separation

SC.L1-b.1.xi — Subnetwork Separation — is one of the 15 CMMC Level 1 requirements. This page gives the exact requirement text, every assessment objective, and what evidence an assessor will ask for.

Last reviewed: October 18, 2026

What this requirement asks

FAR 52.204-21(b)(1)(xi) text:

Implement subnetworks for publicly accessible system components that are physically or logically separated from internal networks.

This is CMMC Level 1 requirement SC.L1-b.1.xi — FAR 52.204-21(b)(1)(xi) — in the System & Communications Protection family. Level 1 is assessed on Federal Contract Information (FCI) by annual self-assessment; no POA&M is allowed — every requirement must be fully met at attestation.

Mapped NIST SP 800-171 requirement

  • 3.13.5 — assessed in full at Level 2

Assessment objectives (1)

  • SC.L1-b.1.xi[a] — Implement subnetworks for publicly accessible system components that are physically or logically separated from internal networks.

Evidence that defends it

Show default-deny rules and explicit permits

Check your readiness

Level 1 self-assessment

FCI · 15 FAR requirements · annual self-assessment · no POA&M

Self-reported readiness only — not an SPRS score, verified result, or certification. A tick means you report satisfying the entire FAR item.

Self-reported score: 0 / 15

Path: close all remaining gaps

15 requirements remain unticked. All 15 must be met; Level 1 has no Conditional or POA&M path. Ticking all items does not establish an official status.

Remaining requirements (15)
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Frequently asked questions

Is SC.L1-b.1.xi required for CMMC Level 1?

Yes. SC.L1-b.1.xi (Subnetwork Separation) is one of the 15 Level 1 requirements from FAR 52.204-21(b)(1). Every assessment objective must be met with supporting evidence.

What evidence satisfies SC.L1-b.1.xi?

Show default-deny rules and explicit permits

Further reading

Related Athena pages and authoritative external references.

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