Repair Active Directory Replication Error 1722 RPC Server Unavailable

Before you begin

Applicable to supported Windows Server/client environments where the named role or feature is installed. Run read-only checks first from an elevated PowerShell or Command Prompt as appropriate. Replace example hostnames, domain names, addresses, ports and paths with values from the affected environment. Record the exact error, timestamp, OS build and scope of impact.

Production safety: obtain change approval and a verified backup before modifying AD DS, DNS, DHCP, firewall, IIS, storage or Hyper-V configuration. Ensure console/out-of-band access before network or remote-access changes.

Symptoms and likely root cause

Repadmin reports error 1722 RPC server unavailable or directory changes do not replicate between domain controllers.

DNS/SRV resolution, RPC endpoint mapper, dynamic RPC ports, routing/firewall, service state, time or replication topology.

Diagnostic commands

repadmin /replsummary
repadmin /showrepl * /errorsonly
dcdiag /test:dns /v
Resolve-DnsName dc02.corp.example.com
Test-NetConnection dc02.corp.example.com -Port 135
Test-NetConnection dc02.corp.example.com -Port 389

Run the commands in order and save the complete output. The commands above are intended to establish the failing layer before a configuration change is attempted.

How to interpret the results

Record source, destination, naming context, last success and exact error. TCP 135 checks the RPC endpoint mapper only; AD replication also needs negotiated dynamic RPC ports and other documented AD dependencies.

Practical correction

Correct stale DNS records, DC NIC DNS configuration, routes and firewall rules using Microsoft AD port guidance. Check NTDS, Netlogon, RPC and DNS services and correlated logs on both DCs. Retry replication only after transport and authentication are healthy.

Make one change at a time. Re-run the failed diagnostic after each change so the cause-and-effect relationship is clear.

Fallback and recovery

Do not demote/re-promote DCs, seize FSMO roles or delete connection objects as a first-line 1722 fix. Preserve system-state backups and restore prior firewall/route changes if access worsens.

Verification checklist

Success: repadmin /replsummary shows no persistent failures and a test object/attribute converges on partner DCs. Port 135 success alone is insufficient.

• Repeat the original failing operation from the affected client/user or service.
• Test from a second approved endpoint or subnet where relevant.
• Review the relevant event log/IIS log after the fix.
• Record the change, actual result and any remaining limitation.

Frequently asked question

Does port 135 being open prove RPC works? No. Dynamic RPC and AD dependencies must also pass.

Official technical reference

Microsoft Learn — diagnose replication failures

Use the official documentation for exact version support, prerequisites and any procedure that differs between Windows Server releases.

Technician field note

This runbook describes a controlled diagnostic path; it is not a universal guarantee that every environment has the same cause. If evidence does not match the expected result, stop and investigate rather than applying unrelated fixes. Do not mark the incident resolved until the original symptom is verified as cleared.