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DHCP Failover & Removed unable to configure new dhcp failover RRS feed

  • Question

  • Greetings and Salutations

    i have and issue with DHCP failover realtionship. At first all is well then undertook windows system updates (as recommneded) and now the DHCP relationship failed and i found out the hard way basically DC1 VM failed to load and DC2 VM didn't do its job so now having issues which resulted in me undertaking a full failover senerio system check, which confirmed me DHCP failover issues. both windows server 2016

    So managed to remove the relationship: which is hard like all relationship but i basically stopped DC2 DHCP server and initialised the deletion of the relationship on DC1, as DC2 was unavailable and undertook the same on DC2 as both failover couldn't contact each other which allowed the dhcp failover relationship removal.

    System State Now: DC1 has full DHCP role with no replication and i have removed DC2 from the dhcp server options, so now only DC1 gives out IP's.

    DC2 has dhcp enable with no scope configured so basically a blank shell waiting to be used. I did go into the DHCP folder and dhcp folder on DC2 and remove all configuration files hence this allowed the clean dhcp on DC2. When i didn't do this it just kept the old scope without the relation.

    DHCP ERROR - Failed Validation of DC2

    pre defined server listed as partners were previously working

    Reconfiguring DHCP failover Error: After removing the failover link on both DC's now when i try to re-create a new failover and enter the ip or host name of DC2 i get an error "Error Encountered during validation of partner server!.

    i have a feeling its related to the DHCP folder setting on DC1, as it still see the old setup but and if so how do i remove without having to re-create the DHCP again which i don't mind doing as the all have 30 day leases and i be up again in 5 mins so no issues with that but hoping i could delete a file or two to resolve, any thoughts anyone??


    UPDATE:

    Stopped DHCP on DC1 and removed all entries in the windows/system32/dhcp folder and recreated the DHCP server with new range, etc and it live and working tried to recreate a failover relationship and it failed with the same error. 

    so both DC's have had the dhcp folders completely wiped removing all traces so i thought, of any past relationship and this is not the case so i think i have to wipe the DC2 and start again.

    update 2:

    WOW madnesss basically all comms between the two DC was lost and i cannot even decommission DC2 from the domain as it cannot contact DC1 so no doing a removal from DC1 by deleting the DC2 from AD and removing an reference to in in DNS and DHCP, etc and will rebuild the server from scratch.

    i'll updated after the rebuild

    Thank you, God speed






    • Edited by CorpCaleCeo Wednesday, September 12, 2018 6:12 PM
    Monday, September 10, 2018 7:16 PM

Answers

  • Much wider issue and will rebuild as it cannot see DC1 to decommission


    Thank you, God speed


    • Edited by CorpCaleCeo Wednesday, September 12, 2018 6:15 PM
    • Marked as answer by CorpCaleCeo Wednesday, September 12, 2018 6:15 PM
    Wednesday, September 12, 2018 6:13 PM

All replies

  • Hi,

    Thanks for your question.

    • The way to dismiss the failover relationship may be the cause of the problem.

    Image

    • For your issue, I will give some basic suggestions:
      Firstly, ensure that you could ping the remote DHCP server.
      Secondly, I test this issue use the admin permission, and have not test by non-admin accounts.
      Lastly, you could refer to link below to configure the DHCP failover:

          https://newhelptech.wordpress.com/2017/06/29/step-by-step-dhcp-failover-in-windows-server-2016/  

    • The worst situation is that you need to redeploy the DHCP server.

    Best regards,

    Travis


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com

    Tuesday, September 11, 2018 3:11 AM
    Moderator
  • thanks for the reply. regarding the image i don't have that option as i cannot create a partner as the DHCP cannot can contact the DC2 but cannot validate it anymore. i can ping all servers, there on a domain and from the images you can see that DHCP server see's the server DC2 however has its an issue with validating so communication is not an issue per say it validating that server from a DHCP point of view.

    As all DHCP servers config, info, etc is kept in the DHCP folder as specified as default and i would like to know if it possible to delete an entry in the folder so it forgets that at some point there was ever a relationship between 2 DC's.

    i'm checking the folder to see if that's possible or worst case i just rebuild it by deleting all info in that folder and starting again


    Thank you, God speed

    Tuesday, September 11, 2018 9:30 PM
  • Hi,

    Thank for your reply.

    It will be a daunting task. Unfortunately the workaround is to perform step by step what the wizard would had done and force said actions:

    • Pick the server you want to keep. Look at your DHCP leases and determine which might be the most complete.
    • Stop the partner DHCP server so only one server is responding to DHCP requests.
    • Try to assign clients from the partner DHCP server back to the server you want to keep. Renew leases so to prevent potential conflicts.
    • You are going to force the removal of the DHCP failover relationship. Because there is no communication the partner server won’t transmit the latest changes and the scope won’t be removed from it. Execute the following command in order to remove the relationship:Remove-DhcpServerv4Failover -ComputerName dhcpserver.bauzas.com -Name SFO-SIN-Failover -Force
    • You will get a warning that says: “Failed to delete the failover relationship <Name of the relationship, i.e. SFO-SIN-Failover> on the partner server <Name of partner server, i.e. dhcpserver2.bauzas.com>”. As I mentioned this is the expected behavior as you cannot communicate with the partner server.
    • Manually delete the scope from the partner server to ensure no conflicts arise if it accidentally becomes active.  

    Best regards,

    Travis


    Please remember to mark the replies as an answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com

    Wednesday, September 12, 2018 8:15 AM
    Moderator
  • I have done all the above. the issue i mention is trying to create a new relationship after i decommissioned the DHCP relationship. I though i made this clear in me question but it seems not.

    (1) DC1 & 2 no longer have a relationship as it been decommissioned

    (2) DC1 is now the only DHCP server serving IP and DNS

    (3) DC2 has a unconfigured DHCP server await a new realtionship

    (4) DC1 can contact DC2 but it cannot validate for a new relationship when trying to re-establish a new failover

    (5) options: ???? hence the question

    My option which i knwo i can do

    (6) Worst case: decommission DC2 complete remove all DC, DHCP, DNS etc and remove from overall domain as a DC adn remove the DC from AD and then undertake a new DC build

    (7) worst case: open the DHCP folder on DC1 and remove all entries and rebuild the DHCP server and try to re-establish failsafe relation

    (8) build a new DC3 and add it and use that as a new failover and decommission DC2 and then rename DC3 to DC 2 and update DNS, Name Servers, Etc


    Thank you, God speed

    Wednesday, September 12, 2018 5:34 PM
  • Much wider issue and will rebuild as it cannot see DC1 to decommission


    Thank you, God speed


    • Edited by CorpCaleCeo Wednesday, September 12, 2018 6:15 PM
    • Marked as answer by CorpCaleCeo Wednesday, September 12, 2018 6:15 PM
    Wednesday, September 12, 2018 6:13 PM