What this requirement asks
Deny network communications traffic by default and allow network communications traffic by exception (i.e., deny all, permit by exception).
This is a CMMC Level 2 requirement in the System & Communications Protection family, drawn from NIST SP 800-171 Rev. 2. An assessor evaluates it objective by objective — every objective below must be supported by evidence, not just described in a policy.
Assessment objectives (2)
- 3.13.6[a] — network communications traffic is denied by default
- 3.13.6[b] — network communications traffic is allowed by exception
What an assessor examines
Examine:
- System and communications protection policy
- procedures addressing boundary protection
- system security plan
- system design documentation
- system configuration settings and associated documentation
- system audit logs and records
- other relevant documents or records
Interview:
- System or network administrators
- personnel with information security responsibilities
- system developer
- personnel with boundary protection responsibilities
Test:
- Mechanisms implementing traffic management at managed interfaces
Evidence that defends it
Show TLS/IPsec settings and scan validation
Check your readiness
Score this requirement against your own environment with the Level 2 self-assessment checklist, or estimate your SPRS score with the free CMMC compliance tool. Self-reported answers are planning signals only — they do not establish a verified or assessor-accepted result.