Description

This article describes the issue of being unable to access the router via the AUX port with a modem (US Robotics) for out of band management.

Symptoms

When trying to get the Auxiliary Port to work with a modem for out of band management, it is possible to dial into the modem; but the login prompt is not provided.

Troubleshooting procedure :

Check the DIP switches settings. US robotics modems have DIP switches; try to set them as follows:

  • DTR normal (up)
  •  Verbal result codes (up)
  • Suppress result codes (down)
  • No echo, offline commands (up)
  • Auto answer on (up)
  • Carrier detect override (up)
  • Load NVRAM defaults (up)
  • Smart mode (down)

The cable type is 9 pin to 25 pin null modem cable.

To configure an AUX port, refer to the following link:

http://www.juniper.net/techpubs/en_US/junos9.5/information-products/topic-collections/swconfig-system-basics/port-console-and-auxiliary-configuring.html

Solution


By default, the modems are set with a variable serial port rate, which allows the modem to change its serial port rate to match the connection rate. For example, if the connection to the modem is 57600 Kbps, it will attempt to talk to the auxiliary port at 57600 Kbps. After changing to a fixed rate of 9600 Kbps and it is saved to NVRAM on the modem, it works with a standard null modem cable.

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