Windows Server 2019 – WFP callout driver blocks RPC and domain traffic – Fix and Prevention

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution — Primary Fix
7. Solution — Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Domain joins, GPO, and management tools fail due to blocked RPC flows.

Environment & Reproduction

Introduced after endpoint firewall driver update with new callout rules.

netsh wfp show state
Get-WinEvent -LogName Security -MaxEvents 100 | Where-Object {$_.Message -match '5152|5157|RPC'}

Root Cause Analysis

Callout classification logic incorrectly denies legitimate RPC-related traffic.

Quick Triage

Confirm policy source and isolate blocked ports/services in logs.

Step-by-Step Diagnosis

Trace WFP layers and identify the deny rule and provider context.

Solution — Primary Fix

Deploy updated callout driver and whitelist required RPC/DC traffic paths.

netsh advfirewall firewall add rule name="Allow RPC Endpoint Mapper" dir=in action=allow protocol=TCP localport=135
Restart-Service MpsSvc

Solution — Alternative Approaches

Use maintenance policy mode with reduced enforcement for domain infrastructure segments.

Verification & Acceptance Criteria

RPC-dependent operations succeed and denied flow events drop to expected baseline.

Rollback Plan

Roll back callout package and restore prior firewall policy backup.

Prevention & Hardening

Implement policy simulation tests for WFP changes before production rollout.

Related Errors & Cross-Refs

Related to NDIS filter packet drops and AD connectivity interruptions.

Related tutorial: View the step-by-step tutorial for Windows Server 2019.

View all Windows Server 2019 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Microsoft Windows Filtering Platform and RPC networking references.