Best of Technical Support

Our experts answer your technical questions.
Modem Question

Can I get two nearby modems to talk over a short connecting line without going through the telco, i.e., going from the phone line connector of one modem to the other with a twisted pair (reversed)? It seems this should work and I think I know the correct AT commands, but I can't get it to work and nobody seems to know the answer. I am not talking about a null modem cable. I want to use this to test out PPP server setups. Thanks for any information. —William Strickfaden, xws99@hotmail.com

This depends on your modems. The phone company normally provides line voltage that modems modulate with their signals to talk to one another. Some modems have been known to work without this voltage, but before you go that route, you can look for a “phone-line simulator”. This device will provide the line voltage and will even ring one end when the other picks up. They're usually not too expensive, or if you're a hobbyist, you can try to build one. Many circuit encyclopedias have simple circuits which do that.

This is the only option. LAN signals have voltage supplied by the devices on each side. You cannot do the same thing with phone connections just by reversing the wires. —Chad Robinson, Chad.Robinson@brt.com

Secure Passwords and PPP Connection

Has anyone had success in establishing a reliable PPP connection from Linux to a Shiva LanRover modem bank(www.shiva.com/remote/d56)? I've been through DejaNews and talked to the Red Hat PPP guru, but so far no luck.

Also, my employer uses SecurID to form part of the password, so it is literally impossible for me to have a static password entry in /etc/ppp/pap-secrets or /etc/ppp/chap-secrets. Is there any way to accommodate passwords that are generated through SecurID? —Steve Masticola, masticol@scr.siemens.com

The dip program has scripting features that include explicit support for SecurID cards. It even understands about the static and variable parts of SecurID passwords, with support for both pieces independently. The script simply says:

securidf fixedpart

to store the fixed part. Later, the script says

securid

whenever the password prompt is recognized; this makes the script stop and prompt you for the variable part, and then dip sends the combined parts to the server. —Scott Maxwell, s-max@pacbell.net

Try using seyon or minicom to see if you can get a login and password prompt. Type ATDTnumbertocall then press enter once you get the CONNECT message. If you can, you should use those to connect, close the application without hanging up the modem, then run pppd by hand:

pppd /dev/modem 57600 crtscts modem noipdefault\
defaultroute

If you don't have a /dev/modem link, substitute it for your serial port. —Marc Merlin, merlin@varesearch.com

LILO Problems

I am a new user. I installed Red Hat version 5.01 for the first time on a partitioned disk (486 system). Immediately after I switch on the message, “Lil” comes up and the system stops. When I use a floppy boot, it is all right. Should I reinstall Linux again, or can I configure properly after it is booted through the floppy? The other partition is Windows 95. I want both options to be displayed while booting. Please help. —Manilal, chirakkal@yahoo.com

You must have had a problem with configuring LILO during the Red Hat install. One possible reason is that your root partition crosses the 1024 cylinder boundary on your disk, and this prevents LILO from booting. There are many other possible problems with IDE disks and the different kinds of translations that your BIOS may be able to do (CHS or LBA head translation). I suggest you try different settings in the BIOS and the linear option for LILO. Also refer to the following LILO HOWTOs:

metalab.unc.edu/LDP/HOWTO/mini/LILO.html
metalab.unc.edu/LDP/HOWTO/mini/Multiboot-with-LILO.html

—Marc Merlin, merlin@varesearch.com

Slow Transfers

I need to mount a 6GB HDD IDE drive formatted for NTFS on my Linux system that will allow me to transfer a 5GB file from the drive to Linux format, so that I can process the data in the UNIX world. I have found a read-only NTFS drive that is under development, but I could not get it to compile. I get an error on a time_t call. I've tried to use FTP to transfer the file, but it goes so slow I'm afraid it would take a week to do the transfer. I also tried to FTP the file to my RS/6000, but that consistently dies at 1.2GB. If I try to use the SAMBA interface, the transfer dies at about 500Mb.

I've also installed AWK on the NT box, but it goes so slow that I can't believe the NT box will stay up long enough to complete the transfer. Help! —Algis Posius, algis@pacbell.net

The 2.2.x kernels already have support for both read/write in NTFS partitions. Even though I've never tried to copy that amount of data, it seems stable enough for the task. Just one question: do you have 5GB of data or a 5GB file? If you have a 5GB file, you are out of luck. The 32-bit version of Linux (and AIX also) can address files only up to 2GB. —Mario Bittencourt, mneto@argo.com.br

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