Multiple BAD_ADDRESS in DHCP showed up again

What is the reason for multiple BAD_ADDRESS in DHCP?  Description - This address is already in use.  I deleted them already few days back.  They came back for some reason.  About eight of them.
And it seems they show up after a an abrupt power outage we had.  Not sure if related.

Server 2016 Domain Controller.
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Tiras25Asked:
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Cliff GaliherCommented:
The most common cause is a rogue DHCP server. Or a DHCP scope with addresses that have also been statically assigned. The DHCP server attempts to assign them to a requesting device and the result is a conflict, and thus a bad address designation.

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DrDave242Senior Support EngineerCommented:
They came back for some reason.  About eight of them.

Are those addresses all in sequence, or are they random?
Tiras25Author Commented:
Thanks Cliff.  I guess I need to find those devices.  Let me think how...

Somewhat in sequence but not really.  
.100
.105
.106
.117
.118
.120
.123
.124
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DrDave242Senior Support EngineerCommented:
If you ping those addresses, do you get a response?

Note that a lack of a response on a given address doesn't necessarily mean that address isn't in use, as there could be a device there with a firewall that blocks ICMP traffic. If you do get a response, though, the address is unquestionably in use by something.
Tiras25Author Commented:
Yes, they are all pingable.  3 of them I can even resolve a hostname with ping -a ipdaddress
JohnBusiness Consultant (Owner)Commented:
Get Advanced IP Scanner (Famatech - Free) and run it. It should give you information about the devices. It does for me.
Tiras25Author Commented:
I'll try thanks John!
Shaun VermaakTechnical SpecialistCommented:
Enable conflict detection with this PowerShell. Most of the times I see BAD_ADRESS it is because of static addresses in a range
Set-DhcpServerSetting -ConflictDetectionAttemps 2

Open in new window

Delete the existing ones with this PowerShell
$DHCPBadReservations = Get-DhcpServerv4Scope -ComputerName $DHCPServer | Get-DhcpServerv4Lease -ComputerName $DHCPServer | Where-Object -FilterScript {$_.HostName -eq 'BAD_ADDRESS'}
$DHCPBadReservations | Remove-DhcpServerv4Reservation -ComputerName $DHCPServer

Open in new window

Owen RubinConsultantCommented:
Is it possible some of the machines in your network have set themselves to static addresses?

If the DHCP server is not aware of those (ie, reserved IP to the MAC address of those machines) then it will give out those IP addresses not knowing that someone has use that same address manually.

You could power down all machines, and bring them up one at a time WITHOUT the DHCP server running, and see if you can ping those addresses. If you can, then they are set manually and now you know which machine is using an address incorrectly.
serialbandCommented:
arp -a  on the command line should show the matching MAC addresses to help you id the system.
Owen RubinConsultantCommented:
Serialband, will arp show multiple systems matching MAC addresses or only the first to answer?
serialbandCommented:
It will show multiple MAC using the same IP.
Owen RubinConsultantCommented:
Thanks. I did not think that would work as I never used it for that. I learned something new today!  :-)
serialbandCommented:
You do have to be on the same subnet to get the correct arp -a results.
Owen RubinConsultantCommented:
That much I could figure out!  :-)
JohnBusiness Consultant (Owner)Commented:
@Tiras25 - Thank you and I was happy to help.
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