Question DHCP Service is not offering IPs all of a sudden

[seema kanwal]

Dear Community,

We have DHCP Service installed on windows server 2019 Server based vm which is also Domain Controller. We have 2 domain controllers here, ho-domain & ho1-domain. Everything was working fine until we started facing Issue with the DHCP Yesterday when it couldn't offer IP To newly procured HP Laptops yesterdy. Afterwards, It also Started happening on all the devices, that no old device was being handed over IP by DHCP.
Below are the steps that we performed. But the DHCP is still up and has showed no abnormal events either and did not crash as well. The only thing it did was to not handover IPs to the Client Machines.

1. We rebooted the Domain Controller ho-domain (which had dhcp role)
2. We restored DHCP Service with 1 days old DHCP Backup on the ho-domain machine.
3. We then thought that the Server might be problematic so we Unauthorized the DHCP role from ho-domain.
4. Next, we restored the dhcp backup on second domain controller ho1-domain and authorized it, it was up though but the issue was still the same. It was not handing over IPs.
5. As our domain controllers are Virtual machines, so we rebooted the Base Machines as well on which these vms are created
6. Then we isolated our network and connected a client device directly to the base Machine of ho1-domain VM, so Incase any Switch or another

intermedite Device was causing Issue it would be bypassed, but it still not resolved the Issue

1. We then Installed the DHCP Role on Third Machine which was a separate physical Machine and since it had Windows Server 2012 in it. We couldn't restore it through DHCP Backup and infact we manually defined scope and everything. Also, it only did few lease.
2. It was all good. But once we tried to manually reseverve the IPs which weere not yet leased , it started causing Issue and not only all reservations became inactive, It sort of stopped leasing IPS as well.
3. Then we installed DHCP Role yet on an other Physical machine and this time we didnot resrve any IP and the DHCP serevr is sort of provong leases. But we didnot manually added reseervations against our mac devices as we had a fear that this third time configured DHCP would also turn weird and stop leasing.

Now I want your help, As I dont see any Major Event in DHCP EventLogs and I dont understand how to resolve this Issue. Its really frustrating. Please help me out in this situation.

Thanks.

 

[Ralston18]

How many existing network devices are there that use DHCP addresses?

How many existing network devices using static IP addresses?

Can you ping devices with static IP addresses? Can any devices be pinged?

How many new laptops? Were the laptops pre-configured with respect to the requirements of the existing network?

What is the available DHCP IP address range? How many reserved IPs are required?

Sketch out a basic network diagram showing all network devices and connections. Label each device by name, MAC, and IP address type, and actual IP address being used.

Look for any network loops that may have been created, any duplicate IP addresses, or incorrect sub-masking.

Use the results of "arp -a" to learn more about what the various network devices are "seeing".

Put as much information as possible into a diagram or other representation of your network. Being able to see the "big picture" along with the applicable details may reveal what is or has happened.

 

[seema kanwal]

Thank you for your Reply but long story short, my DHCP Server is denying the Offering of IP. I checked it through Wireshark, the client keeps asking for the IP but DHCP does not provide it with one. Can you tell me why Is it happening?

 

[bill001g]

My knowledge of using a microsoft domain controller as a DHCP serve is limited so I can provide only basic suggestions.

I am somewhat unclear how you are using DHCP. When you say the server is denying dhcp does your pc try to request a specific IP address from a particular server address.
In most cases when this fails the pc will fall back to stupid mode and send out a broadcast DHCP request that basically says "someone give me any IP address". Does the server respond to this request and is there some problem with the ip it offers ?

If you have used a static assigning of mac addresses to IP in the DHCP server that is the part that I have little knowledge of. Microsoft has change the way domain servers work since I last worked on them years ago.

 

[Ralston18]

On two or three of the clients that are not receiving the IP address run "ipconfig /all" and post the results.

Also run "arp -a" on the clients and the DHCP Server.

From the DHCP Server post its' IP address, the range of allowed DHCP IP addresses, the lease time, and any static or reserved IP addresses.

Are there any DHCP Server logs that may be capturing why an IP address was not provided?

The DHCP Server may be improperly configured or perhaps corrupted in some manner. Or simply configured to not provide an IP address to certain devices.

Does the network have any routers of any sort connected?

 

[nigelivey]

Just as a thought, check the firewall settings on the new machines, make sure DHCP isn't being blocked, it will be under core networking somewhere