Numbering Scheme

A cOCx/STMx interface is identified by the slot/port format, where:

• slot—Number of the slot in which the line module resides in the chassis. In ERX-7xx models, line module slots are numbered 2-6 (slots 0 and 1 are reserved for SRP modules). In ERX-14xx models, line module slots are numbered 0–5 and 8–13 (slots 6 and 7 are reserved for SRP modules). In an ERX-310 router, line module slots are numbered 1–2 (slot 0 is reserved for the SRP module).
• port—Number of the port on the I/O module

  A cOC3/STM1 I/O module has four ports. Each port accepts one pair of SC-style fiber connectors.

  The cOC12/STM4 I/O module has one or two ports. On an I/O module that supports two ports, one port is active (primary) and the other is redundant. Cabling both ports provides a redundant path to the interface. If the active port fails, the redundant port automatically becomes active. You can configure only port 0 on a cOC12/STM4 I/O module. Port 0 accepts one pair of SC-style fiber connectors.

  On I/O modules that support APS/MSP, the port numbers for the working (primary) interfaces are assigned the lower half of the numbered interfaces, whereas the port numbers for the protect (redundant) interfaces are assigned the upper half of the numbered interfaces. For example, on an I/O module that provides one primary port and one redundant port, the working interface is port 0 and the protect interface is port 1.

• APS/MSP channel number—Identifier of the working or protect interface for configuration purposes

  The protect interface is always assigned channel number 0. The working interface is always assigned channel number 1.

For information about installing line modules and I/O modules in ERX routers, see ERX Hardware Guide, Chapter 4, Installing Modules.

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