Edit subnet mask or scope in dhcp server running in windows server - Solved
it's not possible to directly change the subnet mask of an existing DHCP scope in a running Windows DHCP server. Here are the steps: 1. Export the Existing Scope Configuration: Open a command prompt with administrative privileges. Type the following command to export the scope configuration to a text file: netsh dhcp server \\<DHCP_Server_Name> scope <Scope_IP_Address> dump > C:\dhcp.txt 2. Modify the Configuration File: Open the dhcp.txt file in a text editor. Locate the line that specifies the subnet mask (e.g., SubnetMask 255.255.255.0). Change the subnet mask to the desired value. Save the changes to the file. 3. Delete the Old Scope: In the DHCP management console, right-click the scope you want to modify and select "Delete." 4. Import the New Scope: In the command prompt, type the following command to import the modified configuration: netsh exec c:\dhcp.txt 5. Verify the Changes: In the DHCP management console, check if the scope has been re-created with the new subnet mask. Right-click the scope and select "Properties" to confirm the subnet mask change. (Major Point - Ensure that your existing network address and subnet network address remain the same after making changes. If they are not the same, you need to modify the entire network address in the text file. For example, if the original subnet is 255.255.255.0 and the network address is 10.1.10.0, and you change it to 255.255.252.0, then the network address should also be updated to 10.1.8.0. Therefore, you must replace all instances of 10.1.10.0 with 10.1.8.0 in the entire text file (using Ctrl+H for the replacement). Thats it....
DNS duplicate record issue
Currently we are seeing duplicate DNS records for multiple DNS zones. This is specific to our VPN IP scopes, as other scopes do not appear to have this problem. In an effort to correct this issue, as it appears to be occurring from DHCP not being able to update/delete DNS records due to the client being the owner of the record, the below steps have been implemented. This is a smaller environment with approx 1200 endpoints, so the slightly more aggressive DNS intervals is not a concern. DHCP lease time adjusted to 8 days from previously 1 day DNS scavenging adjusted to "No Refresh + Refresh" = DHCP lease - 1 day 3 days (no-refresh) + 4 days (refresh) and 1 day scavenging https://docs.microsoft.com/en-us/archive/blogs/askpfe/how-dns-scavenging-and-the-dhcp-lease-duration-relate I also implemented Dynamic DNS Updates per the below MVP blog, but oddly the owner of all DNS records changed from SYSTEM as the owner to being self owned, rather than being owned by the DHCP server. https://blogs.msmvps.com/acefekay/2009/08/20/dhcp-dynamic-dns-updates-scavenging-static-entries-amp-timestamps-and-the-dnsproxyupdate-group/ The DNS duplicate issue is still occurring, which I'm assuming is due to the DHCP server not owning the DNS records and deleting them when their lease expires or updating when the IP is reassigned. Searched around quite a bit on this one and I'm stumped at this point. Anyone have an thoughts/suggestions to get DNS records to be properly owned by the DHCP server?
Running DHCP Server on Windows Server 2012 Essentials
First published on TechNet on Apr 22, 2013 [This post comes to us courtesy of Rituraj Choudhary from Microsoft Commercial Technical Support]Windows Server 2012 Essentials is enabled to run on a network with the DHCP Server service running on the router.
Move single DHCP scope from one DHCP server to another
Hello I am trying to get a single DHCP scope moved from one DHCP server to another. I am moving DHCP servers with multiple scopes to new servers and the commands I am running now, will export ALL scopes on the server to and .xml file then imported on the new server and this works fine but I have another server with multiple scopes but want to selectively export specific scope(s) only. The commands I am running now are.... To Export. Export-DhcpServer -ComputerName "DHCPSERVERNAME" -Leases -File "C:\temp\DHCP-EXPORT.xml" To Import. Import-DhcpServer -Leases –File "C:\Users\admin\Desktop\DHCP-EXPORT.xml" -BackupPath "C:\Users\admin\Desktop\Backup" –Verbose
DNS suffix is added when using nslookup but not when using ping or browsing
Hi everyone, I am using Windows Server 2016, running DHCP and DNS. I have configured DHCP option 15 to add suffix "abc.de". In the DNS server, I've created a zone called "corp.abc.de" .Entries in that zone should be resolvable only by hostname. In theory, if I want to ping user.corp , this should be resolved as the FQDN user.corp.abc.de . example: Server config: A record: "user" inside the forwarding Lookup zone "corp.abc.de" Client machine: We run the below command that works nslookup user.corp Server: DC.corp.abc.de Address: 10.130.3.254 Name: user.corp.abc.de Address: 10.150.70.11 Then we rung the below command that should also work, but it doesn't. ping user.corp Ping request could not find host user.corp. Please check the name and try again. This however, works on Linux machines, but doesn't work on Windows or MAC. I've tried reinstalling the server (both with DC AD and without). After spending 2 days on this, I'm out of ideas. Any help will be highly appreciated.DHCP server full with unknown and misformed MAC addresses
We're seeing this across multiple customers and now for one it's causing their systems to run out of IPs. They get dozens upon dozens of "Unique ID" registrations of something like: 3139322e3136382e312e31323400 These ONLY show up after doing a reconcile and can be deleted but can't be added to a deny filter. They can be added to a registration but that doesn't solve the problem of them hogging IPs for devices that simply do not exist. I've found a ton of other people talking about this, but no real definitive proof as to what's happening and no real solution other than PHP script found here: https://camratus.com/2017/07/26/deal-with-dhcp-server-ip-exhausted/ I have no desire to install and maintain PHP on every Windows Server nor should we have to. The Powershell command Export-DhcpServer doesn't export these despite being shown in the table. The Powershell command Get-DhcpServerv4Lease does show them, but it truncates them to have ... at the end of the normal MAC length which means I can't use Remove-DhcpServerv4Lease to remove them if I parse the output. If I put the actual long MAC address in the Remove-DhcpServerv4Lease command it will remove it, but they change so I can't just build a list and run it as a scheduled task. Given the plethora of posts and complaints about this I can't understand how 1) Microsoft has no articles I can find on it; 2) Microsoft has no guidance on how fix/stop it; 3) Microsoft hasn't updated DHCP on either Server 2016 or 2019 to resolve the issue. This has apparently been happening since at least Server 2008 R2, though we just recently started having issues with it. One poster here, https://social.technet.microsoft.com/Forums/ie/en-US/b5a40949-e6a0-4e9a-aa71-87b4b61d8edd/2008-r2-dhcp-server-assigning-addresses-to-unique-ids-like-3139322e3136382e33302e31323800?forum=winserveripamdhcpdns, said they traced it to Win7 wifi miniport adapter but in all instances there are no Win7 machines on the network (they're all Win10 Pro). Anyway, the bigger the network, the bigger the problem. Small LANs with a half dozen systems will have a couple in them, while larger LANs with dozens or hundreds of PCs will have so man that the scope will down to 0% available IPs. At this point with one client with about 140 devices on their /24, I'm going to have to convert it to a /23 just to have a DHCP range large enough to allow these registrations. I just want them stopped. BTW, the DHCP log files are logging exactly ZERO of these requests. Anyway, anyone have any idea how to stop this madness without having to either do it manually or resorting to PHP? Thanks!could not start DHCP server Service Error 4312: Object identifier does not represent valid object
Hi All, Good Day!!! i am facing some strange issue is that after import DHCP Scope from this new DHCP server with HA Configured failed to start DHCP service. Its a windows server 2019 with HA. Windows could not start the DHCP server Service on local computer Error 4312: The Object identifier does not represent a valid object i checked winhttp proxy configuration . there is no proxy is configured . Not sure what else need to check. if anyone faced same challenge please let us know the solutions. thanks, Kesavan K M
