MODEM CONFIGURATION

[Anoop R Nath]

Can any one help me,


1> How to configure a GPRS modem in redhat enterprise linux 5 connected in com port.

Thanking in advance ,
Regards,
Anoop.

[Matti_Kurkela · Accepted solution]

The standard PC COM ports are known in Linux OS as /dev/ttySn devices, where n is a number.

COM1 = /dev/ttyS0
COM2 = /dev/ttyS1
...

For the computer, a GPRS connection usually "looks like" a dial-up PPP data connection.

The GPRS modem requires one special setting: the APN (Access Point Name) of the GPRS network you're going to use. The APN is typically set by sending a special initialization command string to the modem.
In a standards-compliant GPRS modem, this command string is:

AT+cgdcont=1,"ip",""

(replace with the correct APN for the GPRS network you're using)
Most modem configuration programs allow you to input custom initialization command strings. This is usually considered an "advanced" setup item, but for a GPRS modem this is a necessity.

After the modem has received this initialization command, the actual connection is started by commanding the modem to dial to number "*99#". (Some Siemens modems might require a longer form: "*99***1#".)

The next step is usually a standard PPP authentication. Often the GPRS network requires no authentication, because the SIM card inserted in the GPRS modem is used for user identification.

Please see RedHat documentation:

http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/Deployment_Guide/s2-networkscripts-interfaces-ppp0.html

http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/Deployment_Guide/s1-network-config-modem.html

RHEL 5 has at least three GUI tools for setting up a dial-up connection: "wvdial", "Network Administration Tool" and "kppp".

If the GUI tool of your choice does not allow you to input a custom initialization command string for the modem, set up the connection first without it and then edit /etc/sysconfig/network-scripts/ifcfg-ppp0.
Add a line like this:

INITSTRING='AT+cgdcont=1,"ip","APN"'

DISCLAIMER: I have set up GPRS modem connection in various other Linux distributions, but never yet on RHEL 5. So I might be wrong on some details. I hope this helps anyway.

MK