Thanks for response.

Here are the details abt my env...

I am migrating db sql2k -->sql2k5 where sql2k5 is running on 2 node cluster. and to balance the node separating the db across two instance (active\active mode) running on same cluster nodes..

Old sql2k instance were using 1433 node & to avoid code changes at app side to SQL to listen same port for both instances running on cluster.

Cluster servername - serverN1\serverN2

1st instance name - sqlvirtualA\instance1 - Port 1433,1434

2st instance name - sqlvirtualB\instance2 - Port 1433,1435

I got the error message for SPM/kerberos authentication as you mentioned in your reply too.

sql error log say ----

"The SQL Network Interface library could not register the Service Principal Name (SPN) for the SQL Server service. Error: 0x2098, state: 15. Failure to register an SPN may cause integrated authentication to fall back to NTLM instead of Kerberos. This is an informational message. Further action is only required if Kerberos authentication is required by authentication policies."

based on this error message NTLM authentication scheme is used once kerberos failed. I queried below statement and result is "NTLM"

"select auth_scheme from sys.dm_exec_connections where session_id=111"

-- SQL instance is coming up properly & and I can make connection both the instances remotely using similar port using query analyser. also connection from app server\clinet have no issue using below connection string.

sqlvirtualA,1433

sqlvirtualA,1434

sqlvirtualB,1433

sqlvirtualB,1435

- app uses dns alias to connect to SQL instances and have no issues as well.

dns alias - sql-db1.fqdn mapped to sqlvirtualA

dns alias - sql-db2.fqdn mapped to sqlvirtualB

My biggest concern\question..

how this will behave going forward?

what idoes MS say for such cinfiguration? and des it a sound proof or suggested seting which can be implemnedted on critical Prod env?

Are you\anone aware about such setting already implement on any env and how its working?

again.. you reponse will be much appreciated. Awaiting your response.

Thanks...