The port number on the module that the operator uses to identify the port. The port numbers on the expansion modules will follow standard numbering, beginning at 1 and incrementing until the last port. The phone ports on the base units, however, are numbered according to how they are collected into 'banks' on the unit. IP Office IP500 The entire front of the product consists of 4 plug-in modules. Each module has its own numbering from 1..12. So from the left: 101..112, 201..212, etc. IP Office IP412 There is no way to plug phones into the unit, so only expansion modules should be present. IP Office IP406v2 The leftmost bank of ports are Digital (DS/DT) and labeled as 1-8 on the product, and so are labelled ports 101..108 in the mib. The next bank of ports are Analogue and labeled as 1-2 on the product and so are labelled ports 201..202 in the mib. The next bank of phones are LAN and labeled as 1-8 on the product. Not phones, so not in this mib. IP Office Small Office Edition The leftmost bank of 4 ports are Trunk ports, and so are not available in this mib. The next bank of 8 ports are Digital (DS/DT), and so are labelled ports 101..108 in the mib. The next bank of 4 ports are Analogue, and so are labelled ports 201..204 in the mib. The next bank of ports are LAN, and so are not available in this mib.