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To access the Cisco AccessPath-VS3 Packet Telephony Concentrator shelves remotely, you must configure a modem for an out-of-band connection to the System Controller.
The configuration is a two-step process:
Step 1 Configure modem support in line configuration mode on the System Controller Auxiliary 0 port. You will use a set of core commands to:
Step 2 Configure the modem itself to function with the System Controller.
This chapter describes the following tasks:
As described in Chapter 4, "Configuring the AccessPath-VS3 System for ISDN and Analog Calls," you must configure the lines to which you attach modems in order to allow dial-in access:
Step 1 Enter enable mode, configuration mode, and then line configuration mode on the Auxiliary 0 port of the System Controller:
Step 2 Configure Auxiliary 0 as follows:
CMS01(config-line)# speed 115200
CMS01(config-line)# flowcontrol hardware
CMS01(config-line)# transport input all
CMS01(config-line)# modem inout
CMS01(config-line)# line 1 32
CMS01(config-line)# speed 115200
CMS01(config-line)# flowcontrol hardware
CMS01(config-line)# transport input all
CMS01(config-line)# modem inout
You have now configured your auxiliary port to support modems.
For testing purposes, enter a password and login local command, although you remove these later:
CMS01(config-line)# password test_password
CMS01(config-line)# login local
For an explanation of the required modem commands, see Table 9-1.
| Command | Purpose |
|---|---|
Sets line speed to the highest common speed for the modem and the System Controller's auxiliary port.1 | |
Sets RTS/CTS2 flow control on the line. | |
Selects all protocols when connecting to a specific line of the System Controller. Restores the default configuration. | |
Configures the line to drop the connection when the CD3 signal is lost (cycle DTR4 to close the connection). The modem dialin command can be used instead of the modem inout command to enhance security because the modem dialin command restricts outgoing connections from the System Controller to the modem. Use the modem inout command during setup so that you can configure the modem from the System Controller, and change to the modem dialin command when testing is completed. |
When you configure modems to function with the AccessPath-VS3 system, you must provide initialization strings and other settings on the modem to tell it how to function with the System Controller.
This section describes the tasks required to configure modems that are externally attached to the AccessPath-VS3 system and includes the following sections:
Before you can configure the modem, you must establish communication with it, which requires terminal access to the modem's command environment. The process of manually configuring a modem is described in the following sections:
You communicate with the modem by establishing a direct Telnet session from AccessPath-VS3 system asynchronous lines to the modem.
To establish a direct Telnet session to a modem, determine the IP address of your LAN (Ethernet) interface, then enter a Telnet command to port 2000 + n on the System Controller, where n is the line number to which the modem is connected. For example, to connect to the modem attached to line 129, enter the following command from an EXEC session on the System Controller:
Router# telnet 172.16.1.10 2129 Trying 172.16.1.10, 2129 ... Open
This example enables you to communicate with the modem on line 129 using the AT (attention) command set defined by the modem vendor.
| TimeSaver Use the ip host configuration command to simplify direct Telnet sessions with modems. The ip host command maps an IP address of a port to a device name. For example, the modem1 2129 172.16.1.10 command enables you to enter modem1 to initiate a connection with the modem, instead of repeatedly entering telnet 172.16.1.10 2129 each time you want to communicate with the modem. |
| Tips |
If you are unable to connect to the modem, check the following:
Modem state: Idle Modem hardware state: CTS noDSR DTR RTS
After you make a direct Telnet connection to the modem, you need to test the connection. Send the modem the AT command to request its attention. It should respond with OK. For example:
at OK
If the modem does not reply to the AT command, check the following:
The direct Telnet session must be terminated before the line can accept incoming calls. If you do not terminate the session, it will be indicated in the output of the show users command when it returns a modem state of ready if the line is still in use. If the line is no longer in use, the output of the show line value command will return a state of idle.
Terminating the Telnet session requires first suspending it, then disconnecting it. To suspend a Telnet session, enter the escape sequence Ctrl-Shift-6 x (press Control-Shift-6, let go, then press x). Enter the disconnect EXEC command to terminate the Telnet session.
To suspend and then disconnect a Telnet session, perform the following steps:
Step 1 Suspend the Telnet session by entering Ctrl-Shift-6 x:
Step 2 Enter the where EXEC command to check for open sessions:
Step 3 After suspending a session with one modem, you can connect to another modem (then suspend it):
Step 4 To disconnect (completely close) a session, issue the disconnect EXEC command:
The following sections describe how to configure an external modem:
This section describes how to determine the correct initialization string for your modem and configure your modem with it.
Modem command sets vary widely. Although most modems use the Hayes command set (prefixing commands with AT), Hayes-compatible modems do not use identical AT command sets.
See your modem documentation to learn how to examine the current and stored configuration of the modem you are using. Generally, you enter AT commands such as &v, i4, or *o to view, inspect, or observe the settings.
A sample modem initialization string for a Microcom modem is as follows:
&fs0=1&C1&D3\Q3&W
The modem initialization strings enable the functions defined in the following sections:
| TimeSaver Initialization strings for other modems are listed in the appendix "Configuring Modem Strings and Chat Scripts" in the Access Services Command Reference and on Cisco Connection Online (CCO) in Tech Tips (http://www.cisco.com/kobayashi/Tech_root.shtm). Note that these URLs are subject to change without notice. |
Lock the speed of the modem to the speed of the auxiliary port on the System Controller.
Modems differ in the method they use to lock the EIA/TIA-232 (serial) port speed. In the modem documentation, vendors use terms such as, port-rate adjust, speed conversion, or buffered mode. Enabling error correction often puts the modem in the buffered mode. See your modem documentation to see how your modem locks speed (check the settings &b, \j, &q, \n, or s-register settings).
Ready To Send (RTS) and Clear To Send (CTS) signals must be used between the modem and the System Controller 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. See your modem documentation to see how to enable hardware flow control (check the settings ', &e, &k, &h, &r, or s-register).
The modem must use the data carrier detect (DCD) wire to indicate to the System Controller when a session has been negotiated and is established with a remote modem. Most modems use the setting &c1. See your modem documentation for the DCD settings used with your modem.
The modem must interpret a toggle of the data terminal ready (DTR) signal as a command to drop any active call and return to the stored settings. Most modems use the settings &d2 or &d3. See your modem documentation for the DTR settings used with your modem.
If a modem is used to service incoming calls, it must be configured to answer a call after a specific number of rings. Most modems use the setting s0=1 to answer the call after one ring. See your modem documentation for the settings used with your modem.
This section defines other settings that might be needed or desirable depending on your modem.
Error correction can be negotiated between two modems to ensure a reliable data link. Error correction standards include LAPM and MNP4. V.42 error correction allows either LAPM or MNP4 error correction to be negotiated. Modems differ in the way they enable error correction. See your modem documentation for the error correction methods used with your modem.
Data compression can be negotiated between two modems to allow for greater data throughput. Data compression standards include V.42 bis and MNP5. Modems differ in the way they enable data compression. See your modem documentation for the data compression settings used with your modem.
After the modem initialization string has been determined, perform the following steps to configure the modem. This example configures a Microcom modem on line 129 (decimal number 2000 + line number 129 = 2129):
Step 1 Map a host name to a decimal port. The port number is 2xxx, plus the number of the tty line. The following example maps port 2129 to the IP address of the Ethernet 0 interface on the System Controller (172.16.1.10):
Step 2 Establish a direct Telnet session to the modem:
Step 3 Optionally, return the modem to its factory defaults:
Step 4 Configure the modem with an initialization string. The following example string is for a Microcom modem:
Step 5 Store the modem settings in NVRAM on the modem:
Step 6 Suspend and disconnect your Telnet session:
| TimeSaver The script-reset line configuration command can automate the configuration of your modems. See the Access Services Configuration Guide, or the "Technical Tips" section on CCO for more information. |
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