Having connection issues out of nowhere in my lab (Azure VMs):

SQL 2016, sp1, cu4 all the way around, Windows 2016 Datacenter

Windows Failover cluster for SQL AG testing.


Default instance (port 1431)

Inst1 (port 1499)


Default instance (port 1431)

Inst1 (port 1499)

From SQLServer-0, I can only connect to the remote instance(s) using tcp:SQLServer-1, 1431 (or tcp:SQlServer-1.kevinsdomain.com,1431)

Same thing for the named instance.

Same thing from SQLServer-1 to SQLServer-0

Ping of just the NetBIOS name works just fine, ping -a resolves the FQDN

None of these are running on port 1433, both server are running SQL Browser under 'NT Authority\Local Service'

This is my test domain, along with a domain controller, DNS, etc.

Windows firewall on each has all of the ports open that are needed, including UDP 1434.

I’m sure there’s something simple I’ve forgotten to check, flush, whatever. Just can’t think of it.


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  • Is the SQL Browser NT service running on both servers? – Solomon Rutzky Mar 28 '18 at 22:42
  • @SolomonRutzky yes – Kevin3NF Mar 28 '18 at 22:48
  • Is this a first time setup? Any service accounts changed? Tried telnet, system restarts? Please check SPN's. – Channdeep Singh Mar 29 '18 at 3:34
  • Considering you're getting an explicit Access is denied error, have you checked the logs on that box? – George.Palacios Mar 29 '18 at 7:22
  • SPNs were missing..added, but no change. This was working previously, now not...obviously something changed but I have no idea what – Kevin3NF Mar 29 '18 at 12:00

Just to clarify your question... you wish to connect to the instance on either server without the need to specify the Port Number?

In that case, did you check if the instance name is added into your SQL configuration manager?

  1. Open SQL Configuration Manager
  2. Expand "SQL Native Client Configuration"
  3. Select "Aliases"
  4. See that if the instance that you wish to connect exists, if no, create the alias for the instance

Hope I do answer your question...

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