User guide

A-46 Cisco 2500 Series Access Server User Guide
Modems
Determine the Modem Initialization String
The initialization string is used to configure the modem for use. A sample modem
initialization string for a US Robotics Courier modem would be as follows:
&b1&h1&r2&c1&d3&m4&k1s0=1
Timesaver Initialization strings for other modems are available from CIO.
Locking EIA/TIA-232 Speed
Lock the EIA/TIA-232 port speed of the modem to the port speed of the Cisco 2500 series
access server. This speed must not change when a session is negotiated with a remote
modem. If the speed of the port on the access server is changed, you must perform a reverse
Telnet to the modem and send an at command for the modem to learn the new speed.
Modems differ in the method they use to lock the EIA/TIA-232 speed. In the modem
documentation, vendors use terms such as, port-rate adjust, speed conversion, or buffered
mode. Enabling error correction will often put the modem in the buffered mode. Refer to
your modem documentation (check the settings &b, \j, &q, \n, or s-register settings).
Hardware Flow Control (RTS/CTS)
RTS and CTS must be used between the modem and the access server to control the flow
of data. Misconfiguring flow control for software or setting no flow control, can result in
hung sessions and loss of data.
Modems differ in the method they use to enable hardware flow control. Refer to your
modem documentation (check the settings \q, &e, &k, &h, &r, or s-register).
Correct DCD Operation
The modem must use the DCD wire to indicate to the access server when a session has been
negotiated and is established with a remote modem. Most modems use the setting &c1.
Refer to your modem documentation for the settings used with your modem.