Networking and DECnet/IP Services
OpenVMS networking spans DECnet (Phase IV and Phase V/OSI) and TCP/IP services. For DECnet, know the node address (area.node) and that SCSNODE/SCSSYSTEMID relate to node identity; DECnet Phase IV uses a 16-bit address, while Phase V uses NSAP addresses and can interoperate with IP. For TCP/IP, know the configuration database (TCPIP$CONFIG), the services (TELNET, FTP, SSH, NTP, DNS), and that the IP stack is configured with a host name, domain, and interface addresses.
Candidates must understand the proxy and access-control concepts: DECnet proxies map remote users to local accounts; TCP/IP proxies serve the same purpose. The proxy database and network access control (e.g., via the NETPROXY/proxy database and the AUTHORIZE proxy entries) determine who can log in remotely. Know that host-based and network-based security interact - a remote login succeeds only if both network access and account authorization allow it.
Traps: confusing the DECnet address with the SCSNODE name; assuming TCP/IP services start automatically without configuration; and forgetting that the network stack must be started (via startup or TCPIP$CONFIG) before remote access works. Also be ready for questions on routing, cluster alias, and the difference between a proxy and a rights identifier.
Rule of thumb: if a remote login fails, check three layers in order - network reachability, the service (TELNET/SSH) being started, and the proxy/account authorization.