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DennisMCSE

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Our company split into 2 separate companies. So we are in the process of migrating to a new infrastructure (DNS, DHCP, etc.) before we migrate the computers to the new domain (there is a trust between the 2 domains for now). On our current domain, the client rarely change IP Addresses. I've known the computers to use the same IP Address for years. So as a shortcut to fix issues, I've used the IP Address of another computer to map a drive (yes I know I shouldn't do that on computers without a fixed IP Address that has a reservation in DHCP).

So when pointing to a new DHCP server, I'm assuming that the new server will issue all new IP Addresses for the clients (the IP ranges, VLAN's,  and scopes are configured exactly the same on the old DHCP server and the new DHCP server). Is there a way to export the old IP Addresses used and import them to the new DHCP server so that the client will use the same IP Address? Or is it just best letting a new IP Address be generated (even though will have to manually check any mapped drives that were mapped with an IP Address instead of hostname)?
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cj_berlin

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Hi,
you wouldn’t usually be importing leases but rather reservations and scope options. AFAIK if you do want to import actual leases you need to replace the whole database then clean up unneeded stuff.

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Evgenij Smirnov

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Pieter

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Reply with quote  #3 
Hi Dennis,

I suggest that you add a line in the logonscript :
net use > \\SERVER\Share\%USERNAME%@%COMPUTERNAME%.log 

After a few days (the time needed that everyone has logged off and on again) you can examine the LOG files to see if there are any mappings using IP addresses.  If so, correct those mappings first, using NetBIOS servername or even better an FQDN. 

BTW: it is possible to do a DHCP export, import.
https://docs.microsoft.com/en-us/powershell/module/dhcpserver/export-dhcpserver?view=win10-ps
https://docs.microsoft.com/en-us/powershell/module/dhcpserver/import-dhcpserver?view=win10-ps

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dennis-360ict

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Reply with quote  #4 
Great advise guys!! I have not much to add, but i read a lot of the support replies and it has some very usefull advice! Just had so sau that.

Btw, if you want to keep the same ip’s, you could:
- make reservations based on the mac adresses.
- put in static ip’s.

But these are not really a solution and if you do these things you could asj yourself why you have a dhcp server at all. Personally i would opt for fixing it like it’s supposed to. So the ligging option and first fix mappings based on dns instead of IPs.

Btw, you can use dns CNAMES to make mappings to changed servernames. This way you could make mappings to old servernames and redirect them to other servers.

Hmm.. seems i had something to add anyway.

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cj_berlin

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Quote:
Originally Posted by dennis-360ict

Btw, if you want to keep the same ip’s, you could:
- make reservations based on the mac adresses.
- put in static ip’s.

But these are not really a solution and if you do these things you could asj yourself why you have a dhcp server at all. Personally i would opt for fixing it like it’s supposed to.

Think old JetDirect print server that would revert to factory default all of a sudden every couple of weeks.

Quote:

Btw, you can use dns CNAMES to make mappings to changed servernames. This way you could make mappings to old servernames and redirect them to other servers.

...and of course re-register all the SPNs to the new servers otherwise you either break Kerberos or have to resort to DisableStrictNameChecking.

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Evgenij Smirnov

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