dhcp failover backup/restore question

2019-10-24

Question

_{Thursday, October 24, 2019 8:44 AM}

I was wondering if the backup and restore process is the same as with no failover setup?

I have some scopes where in their main dhcp is dhcp1 with dhcp2 as secondary and some scopes have their main in dhcp2 with secondary in dhcp1. What would be my strategy in backing up? Will the backup include the configuration, ip leases and reservations? How about the restoration?

Is there are also an option to just backup/restore configurations and reserved IPs?

Also, is there a feature to block mac or ip address?

All replies (3)

_{Thursday, October 24, 2019 10:06 AM ✅Answered}

Hi,

>>I was wondering if the backup and restore process is the same as with no failover setup?

Yes, the process is the same. Windows automatically creates a backup of the DHCP database in %SystemRoot%\System32\dhcp\backup every 60 minutes.

Backup & restore are backuping/restoring the DHCP backup folder which included all DHCP leases, reserved IP addresses, and configured DHCP options.

>>Will the backup include the configuration, ip leases and reservations? How about the restoration?

As I said before, Backup & restore are backuping/restoring the DHCP backup folder which included all DHCP leases, reserved IP addresses, and configured DHCP options.

In DHCP failover , when restore is done, DHCP server will try to sync with the partner servers in the failover relationships.

>>Is there are also an option to just backup/restore configurations and reserved IPs?

There is no such option can only backup/restore configurations and reserved IPs. But we can use commad to export and import DHCP reservations list.

About Backup and Restore DHCP with Failover Configuration – Server 2012, please refer the article:

http://westontech.org/backup-and-restore-dhcp-with-failover-configuration-server-2012/

Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

>>Also, is there a feature to block mac or ip address?

You can configure DHCP Filters to “Allow/Deny” MAC and IP address.

For more details, you can refer this article:

Backup and Restore Windows DHCP Server

Configure DHCP Server 2016 Filters

Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

Hope this can help you, if you have anything unclear, please let me know.

Best Regards,

Ellen

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_{Friday, October 25, 2019 12:52 AM}

Hi Ellen,

If I Enable the Allow in Filters but do not set anything, does this mean that all is allowed?

Is it the same thing also for Deny? Enabling it but not setting anything will it deny all?

If I backup the primary in a hotstandby mode then it goes down unexpectedly like OS corrupt, so the secondary will take the role in giving out ip addresses, when I restore the backup of the primary on the newly built server, what would happen if there are conflicting IPs? Will the primary follow/sync the dhcp leases from the secondary?

_{Friday, October 25, 2019 6:58 AM}

Hi,

>>If I Enable the Allow in Filters but do not set anything, does this mean that all is allowed?

No, all is denied. When the Allow list is enabled, DHCP Server only serves IP addresses to the clients in this list automatically while rejecting all the others.

If clients already had an IP address before filtering, then their IP will not automatically renew when Lease expires. The same as when you enable the deny.

>>what would happen if there are conflicting IPs? Will the primary follow/sync the dhcp leases from the secondary?

There will not be any conflicting IPs. The secondary DHCP will accept the scope data be copied from primary DCHP.

When active server goes down, the standby server transitions into Communication Interrupted state and starts responding to the clients.

Once the active server is up, the standby server retreats into standby mode and stops responding to clients. This facilitates failback of the clients back to the active server.