SQL Server Registration Ports...

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I have 2 SQL Server on remote Network. ServerA and ServerB,
There are firewalls between them. However, the ServerA could regist ServerB
via Enterprise Manager,
but the ServerB could not regist ServerA via EnterPrise Manager....
Both are sitting ON Windows 2003 Server, and 2 Servers Could regist each
other while they stay in Local Lan... .
So How to filter out firewall issues? How many ports are used between SQL
Registration process?


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