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Can someone help me clear something up with regards to AlwaysOn listeners across 2 subnets. Windows Server 2019 SQL Server 2019 This is in Azure

I have created a multi-subnet AG. The listener has 2 IP addresses, one from each region/subnet.

Is it normal that pinging the listener may always time out even when the ping resolves to the IP address that is currently online? Ping replies though when pinging from the the primary itself but anywhere outside of this server does not reply What I'm getting at is that ping is not a reliable tool to confirm connectivity to an AlwaysOn listener.

Regarding connecting to the listener. I have read about the cluster settings RegisterAllprovidersIP & HostRecordTTL for troubleshooting intermittent disconnects. If the client supports MULTISUBNETFAILOVER - Is it safe to say that these settings don't matter? I would think that we only tinker with those settings if the client does not have the option for MULTISUBNETFAILOVER

Any advice?

Thanks

1 Answer 1

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ping is not a reliable tool to confirm connectivity to an AlwaysOn listener.

Correct. DNS will return two IPs for the hostname, and you have no control over which one Ping uses. And ping uses different ports and protocols than TDS, which uses TCP and port 1433 by default.

To test first run nslookup to see the IP addresses, then use test-netconnection to test the IPs. Only one should succeed.

test-netconnection xxx.xxx.xxx.xxx -Port 1433

I would think that we only tinker with those settings if the client does not have the option for MULTISUBNETFAILOVER

Correct.

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  • Thank you very much - Appreciated Oct 31, 2022 at 16:27
  • Does changing the values for RegisterAllprovidersIP & HostRecordTTL change the behavior of clients that does have MULTISUBNETFAILOVER? Nov 10, 2022 at 13:10
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    Changing RegisterAllprovidersIP causes DNS to send only one IP (of the current primary) to the client. Nov 10, 2022 at 13:40

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