BAD_ADDRESS logged in DHCP server Windows Server 2019

Question

Hello,

Recently we got an incident in which clients in one site in one particular subnet not able to connect to network.

Found that IP address is exhausted in that particular scope, when checked found that many BAD_ADDRESSES entries logged in DHCP server . We deleted those BAD_ADDRESS and got free IP's .

But we need to find the reason why BAD_ADDRESS are logged in DHCP server.

Can any one shed some lights on how to investigate?

Answer 1

Hello

Thank you for your question and reaching out. I can understand you are having issues related to DHCP bad address.

BAD_ADDRESS usually indicates an address conflict. This means that the IP address in the lease distributed by the DHCP server has been used by other clients.

It looks like something may be handing out duplicate IP addresses. Do you have any other potential DHCP servers running on the LAN? Maybe a switch/router?

also, run a reconcile on the DHCP database... could be a corrupted DHCP database.

--------------------------------------------------------------------------------------------------------------------------------------

--If the reply is helpful, please Upvote and Accept as answer--

Answer 2

We have only one DHCP server in the environment , when we investigated in realtime when the BAD_ADDRESS entry logged , the onsite person confirmed that he swapped his laptop from wireless network to wired network.

It seems which triggered BAD_ADDRESS in DHCP server at that moment because I confirmed from him through his workstation ID

Will the users switching frequently the networks wireless to wired and vice versa cause this issue?

Answer 3

Today I was checking other scopes , I found in one scope also 3 BAD_ADDRESS entries found.

Is this something can be ignored?

Answer 4

Hello @Techshan

The following is what I found from multihomed-dhcp-clients-may-cause-bad-address-entry-on-a-dhcp-server-in-windows-2000-974ea96f-2c08-dd10-922a-355dcc94b668

This problem may occur when You have one multihomed DHCP client and one DHCP server. This "bad_address" entry is the IP address that was previously assigned to the second network adaptor on the DHCP client.

Assume that nnn.nn.1.1 is assigned to the first network adaptor on the DHCP client
and that nnn.nn.1.2 is assigned to the second network adaptor on the DHCP client.

After you run ipconfig /release ipconfig /renew on the DHCP client, nnn.nn.1.1 is still assigned to the first network adaptor on the DHCP client.

The DHCP server also tries to assign nnn.nn.1.2 to the second network adaptor.

Because conflict detection is enabled on the DHCP server, the DHCP server tries to ping nnn.nn.1.2 before it assigns nnn.nn.1.2 to the second network adaptor on the DHCP client.

Therefore, the DHCP server sends the Internet Control Message Protocol (ICMP) ECHO packet to the media access control (MAC) address of the second network adaptor on the DHCP client.
The DHCP client receives the ICMP ECHO packet and passes it to the upper level.
The DHCP client sends the ICMP ECHO reply packet to the DHCP server from the first network adaptor.
The DHCP server then marks nnn.nn.1.2 as "bad_address".

Solution: You might give a fix address to this dhcp client , or create a script to clear out bad_addresses and make it run regularly.

Best Regards
Karlie

Answer 5

Hi Karlie,

Thanks for your reply , possibly that may be the reason which comes from your comments:

>>>This problem may occur when You have one multihomed DHCP client and one DHCP server<<<<<

I noted yesterday in DHCP server one BAD_ADDRESS for 10.7.0.175 but when I checked today that is not there.

I am seeing that this IP address is assigned to another pc in spite of lease expiration on 9/10/2022

Any idea?