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DHCP failover can not work properly

adam900331 366 Reputation points
2021-01-21T15:30:57.577+00:00

Hello!

I have a test DHCP failover environment with two DHCP server (DHCP1 and DHCP2). One client could obtain an IP address from DHCP1. When I make a failover which means I shut down the DHCP1 (that is the server which assign an IP to my client.) After the DHCP1 shut down, the DHCP2 couldn't control over the active lease and the scope. When the lease time is run out, the DHCP2 couldn't renew the lease, the client is disconnecting from network, discard the IP address and cannot obtain IP from DHCP2. The ipconfig /release and /renew not working.

The test environment:
Lease time: 10 minutes
Switchover time: 60 minutes
MCLT: 5 minutes

I try to reboot the client and restart the DHCP service on DHCP2, but the problem is still being.

Thanks for help!

Windows DHCP
Windows DHCP
Windows: A family of Microsoft operating systems that run across personal computers, tablets, laptops, phones, internet of things devices, self-contained mixed reality headsets, large collaboration screens, and other devices.DHCP: Dynamic Host Configuration Protocol (DHCP). A communications protocol that lets network administrators manage centrally and automate the assignment of Internet Protocol (IP) addresses in an organization's network.
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  1. Candy Luo 12,726 Reputation points Microsoft Vendor
    2021-01-22T09:24:58.59+00:00

    Delete failover relationship and re-configure failover relationship again, check if the issue still occurs.

    If client still cannot obtain IP address from DHCP2, then we need to monitor DHCP packets to narrow down the issue. Check if DHCP client broadcast the lease renew request, whether DHCP2 receives the lease request and responds with a DHCPACK.

    Here is an article talking about DHCP Failover Examples, you can have a look:

    DHCP Failover Examples

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  2. adam900331 366 Reputation points
    2021-01-22T12:54:19.007+00:00

    Thank You. I tried your suggestion. remove the failover and tested the two DHCP server independently. Both DHCP server can serve with IP address to the client. After it, I reconfigured the failover relationship, and the problem is still valid. The client doesn't renew the IP address from the online DHCP2 server.

    I found the following error on the client's DHCP event, when the lease is expired:
    Your computer was not assigned an address from the network (by the DHCP Server) for the Network Card with network address 0xF4B7E22D8721. The following error occurred: 0x79.

    It seems that the client want to obtain the renewal process from the DHCP1 (which is offline).

    When I configure a static IP address, I can ping the DHCP2, and when I configure the client to obtain IP address automatically, the online DHCP2 server can not give IP address.

    When I disable and enable the client's network adapter, the client can obtain IP address from DHCP 2 successfully. Why? It is not realistic in production environment...

  3. adam900331 366 Reputation points
    2021-01-26T08:56:46.347+00:00

    Yes, I think it is an abnormal too.

    The client is Windows 10 Pro 64bit 1909 (virtual machine). I tried the different client and the problem is same too. The two DHCP (DHCP1 and DHCP2) are online. The new client can obtain an IP address. I checked which was the DHCP server to give IP address with ipconfig /all. That was the DHCP2. I disable the network adapter of the DHCP2 and wait to expire the lease. The lease cannot renew on the DHCP1.

    This is the last log in the event viewer which is related to the DHCP failover service:
    The DHCP server DHCP1.domain.net has transitioned to a PARTNER DOWN state for the failover relationship DHCP2.domain.net DHCP1.domain.net and the MCLT period of 300 seconds has expired. The server has taken over the free IP address pool of the partner server DHCP2.domain.net for all scopes which are part of the failover relationship.

    ipconfig /renew can't obtain IP address from DHCP1.

    I don't understand the MS DHCP failover, it mean it isn't failover...

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  4. Candy Luo 12,726 Reputation points Microsoft Vendor
    2021-01-27T08:51:07.817+00:00

    Hi @adam900331 ,

    This is not normal. When you run ipconfig /renew or lease was expired, client should obtain IP address from DHCP partner immediately.

    Please give me some time, I would perform research on this issue and will get back to you as soon as possible. I appreciate your patience.

    If it is urgent, I would suggest you open a case with Microsoft. Generally, in such case, we need to trace and monitor network traffic to analyze the cause. However, analysis of network traffic is beyond our forum support level and due to forum security policy, we have no such channel to collect user log information. So we recommend you open a case with MS Professional tech support service, they will help you open a phone or email case to Microsoft, so that you would get a technical support on a one-to-one basis while ensuring private information.

    Here is the link:

    https://support.microsoft.com/en-us/gp/customer-service-phone-numbers

    Best Regards,

    Candy

  5. Candy Luo 12,726 Reputation points Microsoft Vendor
    2021-02-01T09:42:08.677+00:00

    Hi @adam900331 ,

    I want to share with you my current situations. I reproduced the same symptom in my Hyper-V VM. Stop DHCP1 service, client cannot obtain IP from DHCP2 even run Ipconfig /release & renew or lease expired. I must disable and re-enable client's adapter then DHCP clients can obtain IP address from DHCP2. It's a bit strange, because it can work normally before. I will do more research, please give me more time.

    Best Regards,
    Candy

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