“RPC Server is unavailable” error when requesting a certificate

by Shijaz Abdulla on 06.02.2010 at 00:29

While trying to request a certificate using the Certificates MMC snap-in on a computer running ISA Server, Threat Management Gateway (TMG) or Unified Access Gateway (UAG), you may encounter the following error:

“The RPC Server is unavailable”

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This may be caused due to the RPC Filter in ISA Server/TMG. The RPC filter ensures security by monitoring RPC traffic flowing through the firewall. DCOM traffic is also dropped by this filter. However, DCOM is required to request a certificate.

To workaround this problem, disable strict RPC compliance setting on ISA Server/TMG. Here’s how to do it:

  • Right click on Firewall Policy and choose Edit System Policy .
  • Under Authentication, select Active Directory configuration group
  • Uncheck the Enforce Strict RPC Compliance option.

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  • Click OK and apply your changes.

Of course, you will also need to create a firewall policy rule to allow all traffic from Localhost to Internal. Once you have requested the certificate you can revert these changes.

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You can now request certificates from your ISA Server/TMG computer!