the value of delay configuration on second dhcp server will overwrite the first dhcp server in the DHCP failover.

Question

Hello everybody,

I configure dhcp failover (load share mode) on windows server 2019 with routine steps. Then I come up with an idea , I hope the first dhcp server will be the primary one to serve dhcp client , so I set delay value to 600ms on second server (on advance tab) for (let's say it's) scope A , but keep default value(which is 0) on the first server.

Then issue occurs:
When I make a "replicate failover scopes ..." operation on second server , the delay value for scope A that on first server was overwrite to 600ms, so this will result in no difference between these two server. totally no sense.

However , if I change a new delay value for scope A on first server , then make a "replicate failover scopes ..." operation on first server , its value will not overwrite the delay value for scope A on second server, does it normal ?

1. does setting a delay value for specify scope will achieve my purpose ?
2. I can only make change on the first server , then replicate to second server?

BR
ALEX LU

Answer 1

Hi,

Welcome to Q&A platform.

May I know if your goal is achieving the primary DHCP server is responsible for leasing IP addresses and configuration information to all clients in a scope or subnet and the the secondary server assumes a standby role, with responsibility to issue lease to DHCP clients only the active server becomes unavailable?

If yes, I would suggest you could configure the failover mode to Hot Standby Mode.

For more details regarding of Failover mode, please refer to the following article:

DHCP Failover Modes

As for subnet delay, this is the amount of time in milliseconds that the DHCP server waits before sending a DHCPOFFER. The default value is 0; when having two DHCP servers servicing the same IP subnet, you may change the default settings on your lower-priority DHCP server by increasing the subnet delay value.

I tested in my lab, and found that when I configure subnet delay on the active server and click Replicate Scope, then this value in the partner server will be overwritten. Meanwhile, when I configure subnet delay on the partner server, this value in the active server will also be overwritten. So, if you want to configure this option on the specific server, I would suggest you don't perform Replicate Scope after the configuration.

Best Regards,
Sunny

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