Occasionally, just after connecting, there may be messages in the log that say Magic is same. Sometimes, these messages are harmless, and sometimes one side or the other exits. Most PPP implementations cannot survive this problem, and even if the link seems to come up, there will be repeated configure requests and configure acknowledgments in the log file until ppp(8) eventually gives up and closes the connection. This normally happens on server machines with slow disks that are spawning a getty(8) on the port, and executing ppp(8) from a login script or program after login. There were reports of it happening consistently when using slirp. The reason is that in the time taken between getty(8) exiting and ppp(8) starting, the client-side ppp(8) starts sending Line Control Protocol ( LCP) packets. Because ECHO is still switched on for the port on the server, the client ppp(8) sees these packets “reflect” back. One part of the LCP negotiation is to establish a magic number for each side of the link so that “reflections” can be detected. The protocol says that when the peer tries to negotiate the same magic number, a NAK should be sent and a new magic number should be chosen. During the period that the server port has ECHO turned on, the client ppp(8) sends LCP packets, sees the same magic in the reflected packet and NAKs it. It also sees the NAK reflect (which also means ppp(8) must change its magic). This produces a potentially enormous number of magic number changes, all of which are happily piling into the server's tty buffer. As soon as ppp(8) starts on the server, it is flooded with magic number changes and almost immediately decides it has tried enough to negotiate LCP and gives up. Meanwhile, the client, who no longer sees the reflections, becomes happy just in time to see a hangup from the server. This can be avoided by allowing the peer to start negotiating with the.
3 G and GPRS modems with pppd alone Why not to use a pppd wrapper (like wvdial or similar)?. I particularly switched to direct pppd because my previous software sometimes silently exited instead of reconnecting, as it was configured to do, requiring me to travel to manually perform the reconnection. You may be reading this page by the same reason it was written for: you may have finally concluded that the lesser the layers, the less likely the troubles. Prerequisites and tested hardware The only requirement is the ppp package ( tested). The method described supports easy switching between several carriers and 3 G and GPRS modes. It has been tested and directly works with no modifications (except for the device name) with: Huawei EM770 Mini PCIe modem ( Asus Eee PC 1000 H Go internal integrated modem). Huawei E220 and E1552 external USB dongles. Nokia N73 ( USB tethering; select PC Suite when the phone asks). Nokia CS-15 (lsusb says 0421:0612 Nokia Mobile Phones) Alcatel x310e (carrier: Wind IT) This guide assumes that your modem hardware is properly detected and working. You simply may look at /var/log/messages to discover the device names appeared when the modem is plugged in. Alternatively: root@quark:~ dmesg | grep GSM | grep attached usb 1-6: GSM modem (1-port) converter now attached to tty USB0 usb 1-6: GSM modem (1-port) converter now attached to tty USB1 usb 1-6: GSM modem (1-port) converter now attached to tty USB2 usb 2-2: GSM modem (1-port) converter now attached to tty USB3 usb 2-2: GSM modem (1-port) converter now attached to tty USB4 In this computer there are 2 devices available: a internal 3 G modem (tty USB0) and a external 3 G dongle (tty USB3). The Nokia phones use other device names, like tty ACM0. The extra devices created are useful to get and query the internal modem state while the main one is in use (you may try the cat command on them). To enable some.
Namenull-modem-ppp — Used to setup a PPP connection over a direct serial connection. Synopsisnull-modem-ppp -t TEXT | -tty TEXT [ -start [true]|false ] [ -kill [true]|false ] [ -status [true]|false ] [ -l TEXT | -local-ip TEXT ] [ -r TEXT | -remote-ip TEXT ] [ -m TEXT | -netmask TEXT ] [ -speed TEXT ] [ -o TEXT | -options TEXT ] [ -test-remote [true]|false ] [ -template [true]|false ] [ -sysv-script [true]|false ] [ -h [true]|false | -help [true]|false ] [ - H [true]|false | -help-long [true]|false ] [ -v [true]|false | -verbose [true]|false ] [ -version [true]|false ] Description The null-modem-ppp script is intended to simplify the process of setting up a PPP link between two systems using a serial line as its connection. This script has been successfully used to connect Linux systems (tested on Fedora Core 2 and Fedora Core 3 distributions). To make use of this script, you will need to determine the following: The serial port to be used (like /dev/tty S0). You may omit the /dev/ if desired - we treat tty S0 the same as /dev/tty S0). The baud rate to use for the connection (like 19200). The IP address that the local system will use for the PPP connection (like ). The IP address that the remote end of the PPP connection will be known as (like ). Once your determined the information, you will need to enter it in the configuration file associated with the serial port. For example, one would create the configuration file /etc/sysconfig/null-modem-ppp.tty S0 for the serial port associated with the /dev/tty S0 device. You may also specify options on the command line, but this becomes a bit tedious. Any command line specified options will take precedence over the options specified in the configuration file. If things don't go well, try running it again with the -verbose option. If you use this script on both machines involved in the PPP connection.
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