When you are configuring the server computer, you need to install and configure both mgetty and pppd programs. The mgetty program lets you attend incoming calls and must be configured to run through init daemon in order to take control over the Modem device. By default, inside &TCD; (release 5.5), mgetty isn't configured to start with init daemon so you need to do it yourself (see ). Later, for attending connection requests, you need to configure mgetty to use the pppd program, so the Point-to-Point Protocol (PPP) can be talked and IP packages can be exchange between the client computer and the server computer. Later, you need to configure pppd to adjust it to your needs (see ). Once you've configured both mgetty and pppd programs, the server computer should be ready to attend incoming calls. Taken from mgetty man page: — Mgetty is a smart getty replacement, designed to be used with hayes compatible data and data/fax modems. Mgetty knows about modem initialization, manual modem answering (so your modem doesn’t answer if the machine isn’t ready), UUCP locking (so you can use the same device for dial-in and dial-out). Mgetty provides very extensive logging facilities —. Before using the configuration provided here, it would be useful for you to read the documentation provided by mgetty and SysVinit packages. This will let you to understand what you are configuring. # Run mgetty to control a Multi-Tech (MT5634ZBA-USB) modem attached to # `/dev/ttyAMC0' device. Incoming calls will be attended without fax # initalization. ACM0:2345:respawn:/sbin/mgetty -D ttyACM0 # Automatic PPP startup on receipt of LCP configure request (AutoPPP). # mgetty has to be compiled with "-DAUTO_PPP" for this to work. # Warning: Case is significant, AUTOPPP or autoppp won't work! # Consult the "pppd" man page to find pppd options that work for you. # # NOTE: for *some* users, the "-detach" option has been necessary, # for others, not at all. If your pppd doesn't die after hangup, try # it. # # NOTE2: "debug" creates lots of debugging info. LOOK AT IT if # things do not work out of the box, most likely it's a ppp problem! # # NOTE3: "man pppd" is your friend! # # NOTE4: max. 9 arguments allowed. # #/AutoPPP/ - a_ppp /usr/sbin/pppd auth -chap +pap login debug /AutoPPP/ - a_ppp /usr/sbin/pppd 192.168.1.1:192.168.1.2 In this configuration, we set both local and remote IP addresses to fix the IP information used by computers once the PPP connection has been established. All other options are taken from the options file (see ). If we don't specify both local and remote IP addresses when pppd is initialized, pppd will try to take such information from the first Modem device you configured (e.g., ppp0) and will expect the remote peer to provide its IP address. This situation can introduce some contraditions (e.g., the local and remote address may be on a different network.) that would make the connection to fail. Another issue we might face out would be the netmask specification of the poin-to-point network established between the two computers. Inside the pppd-2.4.4 man page there is no reference to the netmask option, however, there is a mention to it on the sample files installed with it which is quiet confussing. It seems to be required that one of the two computers establishing connection defines the netmask information of the network they are creating. So, to do it on the server computer (the one receiving calls), it is needed to set the netmask definition in the Modem device configuration file of it () along with the local IP address. Otherwise, even local and remote IP addresses be specified through the pppd, the connection will end up having the 255.255.255.255 netmask which would let you ping the computer on the other end but that will not last too long before it fails and iptables seems to get very confused about it. Since we are already using pppd to attend login requests, there is no need to invoke the login program. So, comment the related line as described below. #* - - /bin/login @ I didn't touch this file, but you might need to. I didn't touch this file, but you might need to. Taken from pppd man page: — PPP is the protocol used for establishing internet links over dial-up modems, DSL connections, and many other types of point-to-point links. The pppd daemon works together with the kernel PPP driver to establish and maintain a PPP link with another system (called the peer) and to negotiate Internet Protocol (IP) addresses for each end of the link. Pppd can also authenticate the peer and/or supply authentication information to the peer. PPP can be used with other network protocols besides IP, but such use is becoming increasingly rare —. Before using the configuration provided here, it would be useful for you to read the documentation provided by ppp package. This will let you to understand what you are configuring. # Enables connection debugging facilities. If this option is given, # pppd will log the contents of all control packets sent or received # in a readable form. The packets are logged through syslog with # facility daemon and level debug. This information can be directed # to a file by setting up /etc/syslog.conf appropriately (see # syslog.conf(5)). debug # Require the peer to authenticate itself before allowing network # packets to be sent or received. This option is the default if the # system has a default route. If neither this option nor the noauth # option is specified, pppd will only allow the peer to use IP # addresses to which the system does not already have a route. auth # Specifies that pppd should create a UUCP-style lock file for the # serial device to ensure exclusive access to the device. By default, # pppd will not create a lock file. lock # Specify which DNS Servers the incoming Win95 or WinNT Connection # should use Two Servers can be remotely configured. ms-dns 192.168.1.1 # If this option is given, pppd will send an LCP echo-request frame to # the peer every n seconds. Under Linux, the echo-request is sent when # no packets have been received from the peer for n seconds. Normally # the peer should respond to the echo-request by sending an # echo-reply. This option can be used with the lcp-echo-failure # option to detect that the peer is no longer connected. lcp-echo-interval 30 # If this option is given, pppd will presume the peer to be dead if n # LCP echo-requests are sent without receiving a valid LCP echo-reply. # If this happens, pppd will terminate the connection. Use of this # option requires a non-zero value for the lcp-echo-interval # parameter. This option can be used to enable pppd to terminate # after the physical connection has been broken (e.g., the modem has # hung up) in situations where no hardware modem control lines are # available. lcp-echo-failure 4 # Specifies that pppd should disconnect if the link is idle for n # seconds. idle 60 # Specifies that pppd should disconnect if the link have been active # for n seconds. maxconnect 900 # Disable the IPXCP and IPX protocols. noipx # Secrets for authentication using CHAP # client server secret IP addresses # Specify the client configuration. This is when this manchine calls # someone's else machine and tries to establish a point-to-point # connection. Most of this configuration is handled by the # `system-config-network' utility. # ####### redhat-config-network will overwrite this part!!! (begin) ########## ####### redhat-config-network will overwrite this part!!! (end) ############ # Specify the server configuration. This is when someone's else # machine calls this machine trying to establish a point-to-point # connection. This part of the configuration isn't handled by # `system-config-network' utility. By default, there is one line to # verify client's identity with authenticating it and one line to let # the server computer to authenticate itself with the client computer # in case the client computer requires so. All client computers will # be authenticated through the `faith' user. However, it is possible # to provide anonymous authentication to client computers by using an # empty client identity (as explained in pppd's man page) in order to # restrict the IP address they can use. # "faith" "projects" "mail4u.2k10" "192.168.1.2" #"" "projects" "" "192.168.1.2" "projects" * "mail4u.2k10" Assuming the hostname of the server computer is projects, when a client computer uses the faith username to login on it, the 192.168.1.2 IP address will be assigned to that client computer after a successful authentication. This configuration is just for one Modem device attached to the server computer. In case you have more than one Modem device attached to the server computer, it would be necessary to add one username for each Modem device you have, in order to permit the client computers to connect simultaneously. It is not possible to have two or more computers with the same IP address in the same network. This file contains the same information of cha-secrets file does. See .