Windows Event ID 4983 – Microsoft-Windows-Security-Auditing: IPsec Main Mode Authentication Failed

Start by examining the complete event details to understand the authentication failure context.

1. Open Event Viewer → Windows Logs → Security
2. Filter for Event ID 4983 using the filter option
3. Double-click the most recent 4983 event to view details
4. Note the Source Network Address and Destination Network Address
5. Check the Authentication Method field (Certificate, PreSharedKey, or Kerberos)
6. Record the Failure Reason and any error codes provided

Use PowerShell to extract multiple events for pattern analysis:

Get-WinEvent -FilterHashtable @{LogName='Security'; Id=4983} -MaxEvents 50 | Select-Object TimeCreated, @{Name='SourceIP';Expression={$_.Properties[1].Value}}, @{Name='DestIP';Expression={$_.Properties[2].Value}}, @{Name='AuthMethod';Expression={$_.Properties[3].Value}} | Format-Table -AutoSize

Check the local IPsec policies and ensure they match the expected configuration for your environment.

1. Open Windows Defender Firewall with Advanced Security
2. Navigate to Connection Security Rules in the left pane
3. Review active rules and their authentication requirements
4. Right-click each rule and select Properties to verify authentication methods
5. Check the Authentication tab for certificate or pre-shared key settings

Use PowerShell to examine IPsec policies programmatically:

# View IPsec connection security rules
Get-NetIPsecRule | Select-Object DisplayName, Enabled, Direction, Action | Format-Table -AutoSize

# Check IPsec main mode rules
Get-NetIPsecMainModeRule | Select-Object DisplayName, Enabled, MainModeCryptoSet | Format-Table -AutoSize

# Examine authentication methods
Get-NetIPsecPhase1AuthSet | Select-Object DisplayName, Proposal | Format-List

For domain-joined systems, verify Group Policy IPsec settings:

# Check applied Group Policy IPsec policies
gpresult /h c:\temp\gp_report.html
# Review the IPsec section in the generated report

When certificate authentication is used, verify certificate validity and accessibility.

1. Open Microsoft Management Console (MMC) and add the Certificates snap-in
2. Navigate to Personal → Certificates to view machine certificates
3. Check certificate expiration dates and ensure IPsec certificates are present
4. Verify the certificate chain by double-clicking certificates and checking the Certification Path tab
5. Ensure the certificate has the proper Enhanced Key Usage for IPsec

Use PowerShell to audit certificate health:

# List machine certificates with IPsec EKU
Get-ChildItem Cert:\LocalMachine\My | Where-Object {$_.EnhancedKeyUsageList -match "IP security IKE intermediate"} | Select-Object Subject, NotAfter, Thumbprint | Format-Table -AutoSize

# Check certificate chain validation
$cert = Get-ChildItem Cert:\LocalMachine\My | Where-Object {$_.Subject -like "*YourServerName*"}
$chain = New-Object System.Security.Cryptography.X509Certificates.X509Chain
$chain.Build($cert)
$chain.ChainStatus

Test certificate accessibility from the failing peer:

# Test certificate store access
Certlm.msc
# Navigate to Trusted Root Certification Authorities to verify CA certificates

Check Certificate Revocation List (CRL) accessibility:

# Test CRL download
$cert = Get-ChildItem Cert:\LocalMachine\My | Select-Object -First 1
$cert.Extensions | Where-Object {$_.Oid.FriendlyName -eq "CRL Distribution Points"}

Enable detailed IPsec logging to capture negotiation details and identify specific failure points.

1. Open Registry Editor and navigate to HKLM\SYSTEM\CurrentControlSet\Services\PolicyAgent\Parameters
2. Create a new DWORD value named EnableLogging and set it to 1
3. Create another DWORD named LogFilePath and set the path to C:\Windows\debug\ipsec.log
4. Restart the IPsec Policy Agent service

Configure advanced IPsec logging via PowerShell:

# Enable IPsec audit logging
Auditpol /set /subcategory:"IPsec Main Mode" /success:enable /failure:enable
Auditpol /set /subcategory:"IPsec Quick Mode" /success:enable /failure:enable
Auditpol /set /subcategory:"IPsec Extended Mode" /success:enable /failure:enable

# Restart IPsec services
Restart-Service PolicyAgent
Restart-Service IKEEXT

Use netsh to enable IPsec tracing:

# Start IPsec trace
netsh wfp capture start file=c:\temp\ipsec_trace.etl keywords=19

# Reproduce the issue, then stop tracing
netsh wfp capture stop

# Convert trace for analysis
netsh trace convert input=c:\temp\ipsec_trace.etl output=c:\temp\ipsec_trace.txt

Monitor real-time IPsec events:

# Monitor IPsec events in real-time
Get-WinEvent -FilterHashtable @{LogName='Security'; Id=4960,4961,4983,5453} -MaxEvents 1 | Wait-Event

For complex authentication failures, investigate underlying network and Kerberos issues that may prevent IPsec authentication.

1. Verify network connectivity on IPsec ports using PowerShell:

# Test IPsec port connectivity
Test-NetConnection -ComputerName target_server -Port 500 -InformationLevel Detailed
Test-NetConnection -ComputerName target_server -Port 4500 -InformationLevel Detailed

2. Check time synchronization between IPsec peers:

# Check time sync status
w32tm /query /status
w32tm /query /peers

# Force time sync if needed
w32tm /resync /force

3. For Kerberos authentication issues, examine Kerberos tickets:

# List current Kerberos tickets
klist

# Purge and refresh Kerberos tickets
klist purge
gpupdate /force

4. Analyze network traces for IPsec negotiation failures:

# Capture network traffic during IPsec negotiation
netsh trace start capture=yes tracefile=c:\temp\network_trace.etl provider=Microsoft-Windows-WFP keywords=0x0000000000000010

# Stop trace after reproducing issue
netsh trace stop

5. Check DNS resolution for certificate validation:

# Test DNS resolution for CRL and OCSP endpoints
nslookup crl.microsoft.com
nslookup ocsp.microsoft.com

# Test certificate validation URLs
Certutil -url certificate.cer