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I am facing an issue where I am trying to establish RPC between an on-premise windows server to an azure VM (Windows) by executing the following cmd in the terminal from the source (on-premise windows server):

rpcinfo -p <Azure VM's IP address>

I worked with my network engineer to see if any RPC calls are being blocked by firewall but there is no blocking from the source to the destination. UDP and TCP Port 111 has already been opened. TCP Port 135 is not opened. However my vendor say it is not necessary for RPC.

The terminal is showing this error: rpcinfo: can't contact portmapper: rpcinfo: RPC: Unable to receive; error = 10054

How can I fix the error shown above and establish RPC? PS: I am just a software engineer and not very familiar with this.

Joe
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1 Answers1

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In Microsoft Windows, RPC requires tcp/135 and tcp/49152 through tcp/65535. A packet capture on both ends will show you which ports are being attempted and what is not being received.

Reference:

https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/service-overview-and-network-port-requirements

https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/default-dynamic-port-range-tcpip-chang

https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/configure-rpc-dynamic-port-allocation-with-firewalls

Greg Askew
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  • We are using a COTS product to send data from to the Azure VM using RPC. I checked with the vendor and they said that their own Port Mapper works in the same way as RPC Endpoint Mapper so we open tcp/111 as per advised and didn't opentcp/135 and tcp/49152 through tcp/65535 in the firewall. What does the error mean? Will try packet capture method you recommended. – Joe Jun 19 '23 at 09:01
  • @Joe: If your product uses tcp/135, and then a dynamically assigned high port, your product uses RPC. Your product does not use RPC. As stated, a simple packet capture on both ends will confirm this. It only takes a few minutes. – Greg Askew Jun 19 '23 at 10:02