SC.L2-3.13.6 Network communication by exception
What the standard requires
Deny network communications traffic by default and allow network communications traffic by exception (i.e., deny all, permit by exception).
Quoted verbatim from NIST SP 800-171 Rev 2 (NIST CPRT), which is in the public domain.
Cross-framework mappings
No cross-framework mapping is seeded for this control. That is stated rather than filled in: a mapping nobody authored is worse than a gap you can see.
Track SC.L2-3.13.6 with evidence behind it
In CMDash this control is a row with an owner, a status, uploaded evidence kept with its full history, and an export an assessor can read.