🔍 DEEP TROUBLESHOOTING FOR BLUE EXCLAMATION ON DHCP SCOPE

🔹 1. Check Scope Utilization and Lease Distribution

Run PowerShell on the DHCP server:

powershell

Get-DhcpServerv4ScopeStatistics -ComputerName localhost

This gives:

• Total IPs
• In use
• Available
• Percent utilization

If you’re > 80–90% utilized, that triggers a blue exclamation warning.

Fix: Extend the IP range, or reduce lease duration:

powershell

Set-DhcpServerv4Scope -ScopeId <x.x.x.x> -LeaseDuration ([TimeSpan]::FromDays(1))

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🔹 2. Verify Exclusion Ranges Are Not Overlapping

Run:

powershell

Get-DhcpServerv4ExclusionRange -ScopeId <x.x.x.x>

Then compare with:

powershell

Get-DhcpServerv4Scope -ScopeId <x.x.x.x>

If your exclusions are consuming too much of the usable range, DHCP might have too few assignable IPs left.

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🔹 3. Scope Options Missing or Misconfigured

Run:

powershell

Get-DhcpServerv4OptionValue -ScopeId <x.x.x.x>

Ensure you have at least:

• Option 003 (Router/Gateway)
• Option 006 (DNS)
• Option 015 (DNS Domain Name)

Also ensure there’s no rogue or incorrect DNS (e.g., 127.0.0.1 or public DNS if on internal AD).

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🔹 4. BOOTP Configuration Causing the Warning

If BOOTP is enabled but you didn’t configure BOOTP address ranges, DHCP warns.

Check:

powershell

Get-DhcpServerv4Binding

And in the DHCP MMC:

• Scope > Advanced > BOOTP table
• Disable BOOTP if unused.

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🔹 5. Database Inconsistency or Corruption

Reconcile DHCP database:

• DHCP MMC → Right-click on the Scope or Server → Reconcile
• Or via PowerShell:

powershell

Invoke-DhcpServerv4ScopeReconciliation -ScopeId <x.x.x.x>

If leases in the registry and database mismatch, this clears it up.

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🔹 6. Check for Conflicts Detected by DHCP

DHCP can perform conflict detection (default is 0 pings = off).

Check settings:

powershell

Get-DhcpServerSetting

You’ll see ConflictDetectionAttempts. If it’s non-zero, DHCP is trying to ping before offering leases.

Increase this to catch more conflicts, or set to 0 to reduce delay but lose detection.

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🔹 7. Failover Configuration Issues

If you’re using DHCP Failover:

powershell

Get-DhcpServerv4Failover

Check:

• Failover state (should be NormalComm)
• Partner state
• Conflict between scopes (e.g., both active in Hot Standby)

A misaligned failover sync can trigger a warning.

Try rebalancing:

powershell

Invoke-DhcpServerv4FailoverReplication -ScopeId <x.x.x.x>

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🔹 8. Audit DHCP Logs (C:\Windows\System32\dhcp)

Open DhcpSrvLog-*.log (based on the weekday), look for:

• “NO_ADDRESS_AVAILABLE”
• “BAD_ADDRESS”
• “NACK” responses
• Scope full errors

Or grep it with PowerShell:

powershell

Select-String -Path "C:\Windows\System32\dhcp\DhcpSrvLog-*.log" -Pattern "NO_ADDRESS|BAD_ADDRESS|NACK"

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🔹 9. Event Logs Deep Dive

Check under:

• Event Viewer > Applications and Services Logs > Microsoft > Windows > DHCP-Server > Operational

Filter for:

• Event ID 1041 (Scope low on addresses)
• Event ID 1020 (Scope misconfig)
• Event ID 20292 (Failover sync issues)

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🔹 10. Registry-Level Tuning (Advanced)

Location:
HKLM\SYSTEM\CurrentControlSet\Services\DHCPServer\Parameters

Settings you might tweak:

• DatabaseCleanupInterval (in minutes; default: 60)
• BackupInterval (how often DHCP auto-backs up)
• Check for rogue or invalid scope entries in subkeys under DHCPServer\Configuration

Always back up the registry before making changes.