November 21, 2023 at 4:45 pm
We have AG listener which is configured on a multi subnet. When I do the nslookup on AG lister it does show up active and inactive IP's. Is there a way not to show up the inactive IP's?
November 21, 2023 at 6:47 pm
Why are you concerned with this? if you need fast multi-subnet failover, you have to have two IP addresses.
November 21, 2023 at 7:52 pm
That's a good question. Our VPN will work on active DNS entries sadly due to multi subnet it see's multiple DNS entries with active and inactive IP addresses. I understand manually removing DNS entry would solve this problem. But checking if there is any other workaround/options?
November 21, 2023 at 9:51 pm
Instead of worrying about which IP address the VPN is seeing - just create a separate DNS entry and direct it to the 'active' IP address. If you failover then update that entry to the now active IP address.
As long as you make sure that is documented as part of your failover/DR processes - then you can use that entry instead of directly accessing the listener name. In the future, when you create a new cluster and want to migrate to that cluster - it is simply a matter of updating that entry in DNS to the new cluster and everyone who used that entry are now migrated.
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November 21, 2023 at 10:57 pm
Ok I understand now - you problem is your connection strings. You need to enable multisubnet failover in the connection string, the SQL client goes through a step where it connects to all hosts that resolve, discovers which host is active and then uses that host to connect to. Otherwise netmask ordering would be used by most SQL clients that may never connect the client to an active node. Most SQL clients should be able to do it.
If you can't do that, you can remove the secondary IP address from the listener. You won't have any failover until a DBA or sysadmin intervenes to add it, but you won't anyways without the proper connection string.
November 22, 2023 at 10:04 am
Option1 - Upgrade all your drivers to MSOLEDBSQL (or another driver which supports MSF) and use "MultiSubnetFailover=True" in your connection strings
Option 2 - you could set "RegisterAllProvidersIP" to false to only register the active IP.
Make sure you also reduce the TTL.
You WONT have instant failover in the event of moving to the 2nd subnet, but if your drivers don't support MultiSubnetFailover options, thats the next best thing to be doing than removing IP addresses from the listener.
You WILL have to wait for DNS to update and replicate out an updated A record when the service fails over, as the old IP is deregistered, new subnet active IP registered, pushed to all DNS servers, pushed to all clients, so thats why you need to reduce the TTL so that this process happens more frequently.
November 23, 2023 at 12:27 am
Thank you!
January 12, 2024 at 10:14 am
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