NIST 800-171 3.13.7 (SC.L2-3.13.7): Split Tunneling

Prevent remote devices from simultaneously establishing non-remote connections with organizational systems and communicating via some other connection to resources in external networks (i.e., split tunneling).

NIST SP 800-171 Rev. 2, requirement 3.13.7

CMMC Level 2 practice SC.L2-3.13.7Published 2026-11-11

What 3.13.7 means in practice

A remote device connected to your network must not be connected to another network, such as the internet, at the same time. Configure VPN clients to send all traffic through the tunnel, or otherwise stop the device from bridging the two.

SPRS points and the CMMC POA&M

CMMC Level 2 practice: SC.L2-3.13.7
SPRS points: 1 point. When it is not met, the DoD Assessment Methodology subtracts 1 from the score of 110.
CMMC POA&M: Allowed. It is worth 1 point, and 32 CFR 170.21(a)(2)(ii) admits requirements worth 1 point. Conditional status also needs a score of at least 88, and the item must be closed within 180 days.

Sources: NIST SP 800-171 DoD Assessment Methodology, version 1.2.1 (June 24, 2020), Annex A; 32 CFR 170.21, Plan of Action and Milestones requirements.

What an assessor checks for 3.13.7

NIST SP 800-171A gives one determination statement for 3.13.7.

Determine if remote devices are prevented from simultaneously establishing non-remote connections with the system and communicating via some other connection to resources in external networks (i.e., split tunneling).

NIST SP 800-171A (June 2018), assessment objectives for 3.13.7

Evidence that shows 3.13.7 is met

VPN client or concentrator settings that force all traffic through the tunnel.
Device management settings that stop users from changing the VPN configuration.
A test from a connected device showing internet traffic goes through the tunnel.

How PolicyCortex gathers the evidence

PolicyCortex reads this evidence with the collectors below, read only, and grades 3.13.7 from it. Each line says what the product checks.

Azure: VPN gateways. Reads Azure VPN gateway configuration and checks that split tunneling is prevented for remote access connections.

Related pages

Calculator: SPRS score calculator: mark 3.13.7 and the other 109 requirements and see the score.
Sample package: Sample package: an SSP, a POA&M and an evidence chain the product generated from demonstration data.
Family: All 16 System and Communications Protection requirements (3.13).
Previous: 3.13.6: Deny by Default
Next: 3.13.8: Encryption in Transit
All requirements: All 110 NIST SP 800-171 requirements, by family.

Related records

Guides and articles describe the work. The evidence that work produces is described in three proof pages, the architecture page, and the two pages on authorization.

proof.state: Proof of State. What the environment was, as of a date someone else picks: point-in-time records, content hashed and chained.
proof.change: Proof of Change. Who or what altered the environment, under what authority, with before and after state hashes.
proof.agency: Proof of Agency. What a machine was permitted to do before it acted, what it did, and what would have stopped it.
architecture: Architecture. How the chain is built and where the evidence is stored in each delivery mode.
authorization: Continuous ATO. How an authorizing official's decision is recorded with its package, and how the authorized system is checked against it every hour.
baseline: NIST SP 800-53. The Low, Moderate and High baselines as evidence, with the SSP, SAR and POA&M generated from one record.