Internal FQDN issue when setting up DR site

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phantom-2974 asked Apr 6, '22 LimitlessTechnology-0326 answered Apr 13, '22

Internal FQDN issue when setting up DR site

Hi all,

Im trying to setup a DR site as follows: Server Net 192.168.0.0/24 Server DR Net 192.168.40.0/24 USER Net 192.168.10.0/24 Between the prod & dr their will be an IPsec tunnel so that when I failover my servers in the server network to the dr server network, the user network can communicate with the Server DR Network. For e.g, I have a file server (filesvr) (192.168.0.10) that I want to failover to the DR. The file server ip address will change to 192.168.40.10. In my DNS server I will need to add another A record pointing filesvr.abc.local to 192.168.40.10. The issue is with the round robin load balancing that is the default action of Windows Server when it see 2 A record with the same FQDN pointing to 2 different IP addresses. When failing my File server to the DR, added my A record sometime I can connect to my file server from the user network by its FQDN (filesvr.abc.local) sometime it just times out ! When doing nslookup from the PC in the User network, sometime the 1st IP address is 0.10 & 2nd IP address is 40.10 & some over time is the reverse. Ive been tackling this issue for quite a while & any help would be much much gratefull !!!

Thanks :)

windows-server windows-dhcp-dns

dns.png (26.7 KiB)

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Answer 1 · 2022-04-13T07:22:07.683Z

LimitlessTechnology-0326 answered Apr 13, '22

Hi phantom-2974,

There is no way of prioritising an A record without something like Dyn/Cloudfare/Route53 etc doing some management up front.

You can have both ip-addresses listed as A records and DNS will load balance across to the two addressess to a greater or lesser degree. I believe this is what you’re seeing.

What you'll need to do is to drop the TTL down as low as you can, at least the time period of the current TTL before you make the change.

So if the TTL is 8 days then you need to drop the TTL to a few minutes (or lower) at least 8 days before you flip the records.

Whether this is practical for DR, I’m not sure?

I hope this answers your question.

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