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# Cabling the SRP I/O Module

Before powering up the router, you must set up a management console. The console enables you to communicate with your system during the power-up process and to manage your system using the command-line interface (CLI).

When connecting a console directly to the SRP I/O module, use a cable appropriate for your terminal connector. The cable must have a female DB-9 connector to attach to the RS-232 port on the SRP I/O module. See Figure 24 and Figure 25.

The console port is considered a data terminal equipment interface (DTE). Direct connection to a terminal or PC (which also have DTE interfaces) requires a crossover cable.

| Note: The alarm function on the SRP I/O module is currently not implemented.

Only ERX-7xx and ERX-14xx models have external timing ports and alarm leads located on the SRP I/O module. All ERX routers have console ports located on the SRP I/O module. See Table 7 for details on each component.

Table 7: SRP I/O Ports

Port | Description
--- | ---
Alarm leads (ERX-7xx and ERX-14xx models only) | Six terminal blocks for external alarm contacts; use a minimum 26-AWG for each (currently not implemented)
External timing ports (ERX-7xx and ERX-14xx models only) | Two 3-pin wire-wrap posts for US external clock sources; primary (A) and secondary (B) Two BNC connectors for E1 clock sources; primary (A) and secondary (B)
Management console ports | One 10/100Base-T Ethernet management port with an RJ-45 connector One RS-232 console port with a DB-9 connector for VT100 management access

## External Timing Ports

| Note: This section applies to ERX-7xx and ERX-14xx models only. The ERX-310 router does not support external timing.

The SRP I/O module has two input ports for external clock sources. These ports provide a way to ensure that the router system clock remains synchronized with the network's system clock. The primary clock is labeled A; the secondary, redundant clock is labeled B.

Use the connectors appropriate for your locale (European or North American standard):

- European—Two 75-ohm E1 2.048-Mbps inputs with BNC connectors
- North American—Two 100-ohm T1 inputs with three pin wire-wrap connectors. Pins are labeled T (tip), G (ground), and R (ring). We recommend using 26-AWG wire minimum.

  | Note: Use shielded cables to connect the external clock sources to the clock source input ports.

  Figure 24: SRP I/O Module for ERX-14xx Models

To connect the clock source input ports:

1. Depending on the connector type, complete one of the following tasks:
   - E1: Attach the BNC connector to Clock A's external timing port.
   - T1: Wrap the tip wire on pin marked T of Clock A's external timing port, the ground wire on G pin, and the ring wire on R pin.

     | Note: You can use a wire-wrap gun to attach wires to pins.

2. Attach the opposite end of the external timing cable or wires to your network's clock source A.
3. Repeat Steps 1 and 2 for the Clock B connections.

## Management Ports

| Note: This section applies to all ERX routers.

The Console section of the SRP I/O module has two ports for management access. (See Figure 24 and Figure 25.)

- The 10/100Base-T Ethernet port accepts an RJ-45 (male) connector, providing an out-of-band connection for LAN access through a Telnet session or SNMP.
- The RS-232 port accepts a DB-9 (female) connector for direct CLI access from a console terminal.

  The console port is considered a data terminal equipment interface (DTE). Direct connection to a terminal or PC (which also have DTE interfaces) requires a crossover cable.

  Figure 25: SRP I/O Module for the ERX-310 Router

See Accessing ERX Routers for more information about management access.

### Connecting to the Network

To connect the router to the network:

1. Insert an Ethernet cable (RJ-45) connector into the 10/100Base-T (RJ-45) port on the SRP I/O module until it clicks into place.
2. Connect the other end of the cable to the appropriate Ethernet network for an out-of-band connection.

### Connecting to a Console Terminal

When you connect a console directly to the router SRP I/O module, use a cable appropriate for your terminal connector. The cable must have a female DB-9 connector to attach to the RS-232 port on the SRP I/O module.

To connect the console to the SRP I/O module:

1. Insert the female DB-9 connector into the RS-232 port, and tighten the screws.

   | Caution: Do not overtighten the screws.

2. Connect the other end of the cable to your terminal's serial port (VT100/ANSI).

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