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DNS Dynamic Update

Posted on 2016-07-29
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I would like to understand some things more clearly.

Lets say I have servers and domain controllers with static IP addresses.  What does Dynamic Update really do for me?  How does it help anything in the case of the servers/domain controllers?  Is it ok to turn OFF Dynamic Updates?  Would it hurt anything?

Is there a best practice for having Dynamic Update turned on?  

Thanks in advance!

Dan
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Question by:Danny Verrazano
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by:Paul MacDonald
Paul MacDonald earned 400 total points
ID: 41734647
"Lets say I have servers and domain controllers with static IP addresses.  What does Dynamic Update really do for me?"
Nothing.

"How does it help anything in the case of the servers/domain controllers?"
It doesn't.

"Is it ok to turn OFF Dynamic Updates?"  
Yes.

"Would it hurt anything?"
Potentially.

"Is there a best practice for having Dynamic Update turned on?"
Dynamic updates is the method where a DHCP client updates DNS with its IP information, without the help of the DHCP server.  There are few risks to Dynamic Updates on a network you control.   On a less private network, you might want to turn off Dynamic Updates.
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by:Danny Verrazano
ID: 41734654
"Would it hurt anything?"
 Potentially.


Can you explain or give examples of what could potentially be impacted?  

What exactly does a server/domain controller with static IP addresses do with Dynamic Update??  I am guessing maybe a server will update the timestamp on the record in DNS to prevent it from ever being scavenged??  Does it work that way at all?
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by:Danny Verrazano
ID: 41734670
Also, would I be correct in saying that a domain controller would NOT be able to re-register SRV records when restarting netlogon service or when the domain controller is restarted??  That functionality would be gone correct?  If so, what impact could that have and is there anything else that could be impacted?
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by:Paul MacDonald
ID: 41734826
"Can you explain or give examples of what could potentially be impacted?"
It's unlikely, but a scenario could exist where two devices assert to DNS that they have the same IP address.

"What exactly does a server/domain controller with static IP addresses do with Dynamic Update??  I am guessing maybe a server will update the timestamp on the record in DNS to prevent it from ever being scavenged??  Does it work that way at all?"
Dynamic Update is just the process whereby a client updates DNS directly, without the intervention of a human or DHCP.  

DNS records are not scavenged the way DHCP leases are.


"Also, would I be correct in saying that a domain controller would NOT be able to re-register SRV records when restarting netlogon service or when the domain controller is restarted??"
This is an interesting question.  I would guess there's no way to stop a Domain Controller from updating DNS since generally every DC is also a DNS server.  The idea of a DNS server that's unable to register records in its own database seems unlikely to me.
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by:Danny Verrazano
ID: 41734888
So, what about in the case of NOT using Microsoft AD integrated DNS??    So the domain controllers are not actually DNS servers.  There is an external DNS infrastructure?  

Does anyone know what happens if Dynamic Update is turned off?  Will domain controllers no longer be able to automatically register SRV records when you restart netlogon service?  OR what if you just do ipconfig /registerdns??  Does that rely on Dynamic Updates as well?
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footech earned 1600 total points
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The advantage with dynamic updates, even with clients that are configured with static IPs, is that when it comes time to decommission the static server, if you've got DNS scavenging running, you don't have to spend time cleaning up their DNS records.  And if the static IP changes, likewise its record can be updated automatically instead of having to do it manually.

And yes, the server updates the timestamp on the record to prevent it from being scavenged.
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by:Danny Verrazano
ID: 41735113
Thanks to all who contributed
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