You may already that using "iisreset (server name) /restart" can restart IIS services on that remote server. But why such a command can give you this error message?
>iisreset myserver /restart
The RPC Server is unavailable.
I go ahead and turn off Windows Firewall on my server and now everything is fine. This reveals that actually iisreset was blocked by one of the rules.
Actually DCOM related applications need more attention than I showed above. Please follow this article to set up DCOM port range and firewall rules.