BizTalk Install: "RPC server is unavailable"

I'm in the process of upgrading BizTalk 2009 to 2010. The new BizTalk environment is a two-server active/active environment - the operating system for both aren't using a clustered configuration. The SQL back end is a separate tier (SQL Server 2008R2).

The first BizTalk tier went flawless with the install and configuration. The second tier installation was successful as well.

However, when I tried to configure the second tier, I got the error "(RPC: 0x800706BA: The RPC server is unavailable.) (SSO)" when trying to Join to the existing Enterprise SSO.



There is a bit of documentation out there, and most of it led to information on MSDTC issues. One of the configurations within the BizTalk install is to ensure that the DTC rules are enabled within the firewall configuration. Those were enabled, yet I still recieved errors.

A Microsoft tool called DTCPing, helped me out considerably. I copied the executable to my app tiers and also to our SQL Server tier. You have to run them all simultaneously on each tier. I was able to ping from my BizTalk Sever tier to SQL, but I couldn't successfully ping in the opposite direction.

Hmmm, firewall?

Initial test: Turn the firewalls on the BizTalk app tiers off. Restart the DTCPing process. SUCCESS with ping!

So now we know it's a firewall issue. A new rule added to the firewall was the fix.

As a side note, Chris Forster does a decent job describing some background to MSDTC and SQL.