Server Technology Master vs Link & Expansion PDU’s Differences Explained

Server Technology manufactures PDU’s offering many different models and features. They will refer or classify their PDU’s as a “Master” PDU or a “Link” PDU or an “Expansion” PDU. This article will explain the differences between these terms.

Link PDU Connects Only to a Master PDU

Server Tech’s Smart or Switched PDU’s can pair or “link” with an “expansion” PDU unit thereby creating a master PDU and a link PDU. A master PDU can connect to your network while a link PDU only connects to a master PDU.

Master PDU

A “Master” PDU is the control unit that will enable the full capabilities of Server Technology PDU’s. The critical features that a Master PDU provides is its network monitoring and switching functions (if applicable to that model). These key features provide access to valuable data and the ability to remotely switch outlets on and off through connections including HTTP(S), SSH, Telnet, SNMP, (S)FTP, SMTP, Syslog, LDAP(S), RS-232 serial, and more. A Master PDU can function without a Link PDU.

Link or Expansion PDU

Server Technology uses these terms interchangeably. In other words, a Link PDU is the same thing as an expansion PDU. We’ll refer to them as Link PDU’s for simplicity. A Link PDU attaches to a Master PDU through an RJ-12 Port, thus making it available to be accessed remotely.

A Link PDU can still provide power without a Master. However, without a Master PDU connected to it, you’ll lose powerful features such as network monitoring and remote switching. This is due to a Link PDU’s lack of network connectivity.

The key takeaway is that a Master PDU is always preferably to a Link PDU for standalone use.

Physical Differences

A Master and a Link PDU are almost identical in appearance. They will usually be the same size, have the same output connections, and have the same power cords.

A Master PDU will have extra connection ports: (1) a network RJ-45 port, (2) RS-232 console port, or (3) an Auxiliary port.

Look at a PDU’s part numbers. If the part numbers start with CS, CW, CWG, C1S, C2S, C1SG, C2SG, C1W, C2W, C1WG, C2WG, PDV, STV, then they are Master PDU’s. The main letters to look for are “S”, “W”, “D” and “T”.

While link PDU’s will have starting part numbers of: CL, CX, CXG, C1L, C2L, C1XG, C2XG, C1X, C2X, C1XG, C2XG, PEV, and SEV. Letters that indicate a Link PDU are “X”, “L”, and “E”.