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We have an OLD sbs 2003(SERVER) and a new server 2012R2(SQLSRV) as a member server. &nbsp;SQLSRV is running SQL Express 2014 for a line of business DB. &nbsp;In the client app, the path &nbsp;to the db is \\SQLSRV\sqlexpress but it runs painfully slow. &nbsp;If we change the path to \\192.168.20.12\sqlexpress<wbr /> then it performs properly. &nbsp;<br />
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The client PC's can ping SQLSRV but it will resolve to an IPv6 address however we can also ping SQLSRV -4 and it will resolve the v4 address.<br />
IPv6 is not implemented on SERVER, nor are there any v6 addresses appearing in DNS on SERVER. &nbsp;All machines point to SERVER for DNS.<br />
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So.....<br />

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why are the clients resolving this v6 address if DNS has no record of it?
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since, apprently, they can connect uding thev6 address, why is it having such an impact on speed?
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We have an OLD sbs 2003(SERVER) and a new server 2012R2(SQLSRV) as a member server.  SQLSRV is running SQL Express 2014 for a line of business DB.  In the client app, the path  to the db is \\SQLSRV\sqlexpress but it runs painfully slow.  If we change the path to \\192.168.20.12\sqlexpress then it performs properly.  

The client PC's can ping SQLSRV but it will resolve to an IPv6 address however we can also ping SQLSRV -4 and it will resolve the v4 address.
IPv6 is not implemented on SERVER, nor are there any v6 addresses appearing in DNS on SERVER.  All machines point to SERVER for DNS.

So.....
why are the clients resolving this v6 address if DNS has no record of it?
since, apprently, they can connect uding thev6 address, why is it having such an impact on speed?

IPv6 address being returned for SQL server causes speed issues

The Domain Name System (DNS) is a hierarchical, globally distributed system responsible for associating the name of a computer, service or other resource into an IP address for connecting to the Internet or a private network. Most prominently, it translates domain names to the numerical IP addresses needed for the purpose of computer services and devices worldwide.

Transmission Control Protocol/Internet Protocol (TCP/IP) is the set of networking protocols that define end-to-end connectivity specifying how data should be packeted, addressed, transmitted, routed and received at the destination. This functionality is organized into four abstraction layers which are used to sort all related protocols according to the scope of networking involved.

TCP/IP

Microsoft SQL Server is a suite of relational database management system (RDBMS) products providing multi-user database access functionality.SQL Server is available in multiple versions, typically identified by release year, and versions are subdivided into editions to distinguish between product functionality. Component services include integration (SSIS), reporting (SSRS), analysis (SSAS), data quality, master data, T-SQL and performance tuning.