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Linux PPP FAQ
Al Longyear, longyear@netcom.com
v1.13, 9 December 1996This document contains a list the most Frequently Asked Questions (FAQ) about PPP for Linux (and their answers). It is really not a HOWTO, but is in \classical\ Question / Answer form. We have a different document which represents the PPP-HOWTO. It is written by Robert Hart.
1. Preface
2. General information
- 2.1 What is PPP?
- 2.2 My university (company) does not support PPP. Can I use PPP?
- 2.3 Where is PPP?
- 2.4 I just obtained PPP. What do I do with it?
- 2.5 Where are additional sources of information for PPP?
- 2.6 Would someone please send me scripts for PPP so that I may see how they are written?
- 2.7 Where should I post questions about PPP?
- 2.8 The PPP software doesn't work. HELP!!!
3. Other implementations
- 3.1 Do you know of a implementation for PPP other than Linux? I would like one for HP-UX, or AIX, or ... (you fill in the blank)?
- 3.2 Did you know that there is a program called \dp\?
- 3.3 What RFCs describe the PPP protocol?
4. Compatibility
- 4.1 Can PPP talk to a SLIP interface?
- 4.2 Which is better? PPP or SLIP?
- 4.3 Is CHAP or PAP better for authentication?
- 4.4 What about CHAP which Microsoft uses with Windows NT?
5. Authentication files
- 5.1 What goes into the /etc/ppp/pap-secrets file? Do you have a sample? Or, my ISP requires that I use PAP. How do I do that?
- 5.2 What goes into the /etc/ppp/chap-secrets file? Do you have a sample?
6. Construction problems
7. Problems running pppd
- 7.1 pppd says that version 0.0.0 is out of date
- 7.2 pppd says that that the kernel is not configured for PPP. I know that I enabled the option and built the kernel.
- 7.3 pppd wont run unless you are root
- 7.4 unable to create pid file: no such file or directory
- 7.5 /etc/ppp/options: no such file or directory
- 7.6 Could not determine local IP address
- 7.7 Could not determine remote IP address
- 7.8 I keep getting the message to the effect that the magic number is always NAKed. The system will not connect.
- 7.9 protocol reject for protocol fffb
- 7.10 The PPP software connects, sends quite a few frames, but still does not seem to connect. Why is that?
- 7.11 The /etc/ppp/ip-up scripts won't work.
- 7.12 I can't execute /etc/ppp/ip-up: Exec format error
- 7.13 How do I use PPP with a system which uses dynamic IP assignments? It assigns a different IP address to me with each call.
- 7.14 How do I know what IP address was given to me when it is dynamically assigned?
- 7.15 I just upgraded my system and now pppd reports that the option -v is not supported. Why?
- 7.16 The pppd process reports that it won't replace the existing default route. How do I get it to use the default route?
- 7.17 When I run pppd it says that support is not in the kernel.
- 7.18 How do I use PPP and a local network at the same time?
- 7.19 Can I use the same local IP address for each line of a PPP server?
- 7.20 How do I find my local IP address??
- 7.21 I can't connect to the merit network.
8. DIP
9. Process termination
10. Data Transfer related issues
- 10.1 The ftp transfers seems to die when I do a \put\ operation. They will work correctly if I \get\ a file. Why?
- 10.2 How do I use XON/XOFF for flow control?
- 10.3 The modem seems to always connect at a strange rate. When I use minicom, the modem will always use 14400. However, PPP is using 9600 or 7200 or even 2400. How do I fix this?
- 10.4 The ftp transfers seems to be very slow when I do a \get\ operation. The \put\ operation is much faster. Why?
- 10.5 The proxyarp function fails to find the hardware address.
11. Routing and other problems
- 11.1 My route to the remote keeps disappearing! It last for about 3 minutes and then the route just goes away. Help!
- 11.2 I would like to attach my other computers on my network to the Internet through my PPP connection. I have only the one IP address which is assigned to me from my service provider. (It may even have been dynamically assigned.) How may I do this?
- 11.3 I can reach the remote server, but I can not get anywhere else.
- 11.4 I have a default route and I still can't get anywhere else! Now what?
- 11.5 I can not ping my local IP address
12. Interactions with other PPP implementations
- 12.1 How do I connect to a Windows NT server?
- 12.2 I tried to use MSCHAP or PAP with Windows NT and it fails with "E=691". Now what?
- 12.3 How do I support Windows 95?
- 12.4 I am using a Trumpet (for MSDOS) and the connection simply terminates. Why is this happening?
- 12.5 I am using dp-3.1.2 (with SunOS) and the system will not allow me to use anything but ping, or nslookup. Why is this happening?
- 12.6 My provider wants to use a dynamic DNS address which is not the same with every connection. Yet, Linux wants just one address in the /etc/resolv.conf file. This works with Microsoft Windows 95, but how do I make it work with Linux?
13. Other messages written to the system log
- 13.1 Alarm
- 13.2 SIGHUP
- 13.3 SIGINT
- 13.4 Unknown protocol (c025) received!.
- 13.5 Unknown protocol (80fd) received!.
- 13.6 The connection fails with errors \ioctl(TIOCGETD): I/O error\ or \ioctl(PPPIOCSINPSIG): I/O error\. What now?
- 13.7 Sometimes the messages \ioctl(PPPIOCGDEBUG): I/O error\, \ioctl(TIOCSETD): I/O error\ and \ioctl(TIOCNXCL): I/O error\ occur. Why?
- 13.8 My ifconfig has strange output for PPP.
- 13.9 The file /proc/net/dev seems to be empty
- 13.10 The kernel reports that the PPP devices are being unlinked when the system is being started.
- 13.11 I just checked /proc/net/dev and there are no PPP devices. Where did they go?
14. Network routing issues (using PPP as a \cheap\ bridge)
- 14.1 Slattach and ifconfig don't work as they do with SLIP
- 14.2 I want the route to the network and not the route to the host.
15. Other features and protocols
- 15.1 What about support for \demand dial\
- 15.2 What about \filtering\
- 15.3 How about IPX?
- 15.4 How about NETBIOS?
- 15.5 I need ISDN support. Is there any?
- 15.6 I would like multi-point support. Is there any support?
- 15.7 How about just standard synchronous PPP?
16. Miscellaneous
17. Questions about chat
- 17.1 My modem wont dial when I run chat
- 17.2 The modem dials only on every second attempt
- 17.3 The chat script stops after sending the account name and it never receives the password prompt.
- 17.4 The chat script stops before finishing and fails to make the connection
- 17.5 When I attempt to run chat, it says that the -l parameter is invalid. Why?
- 17.6 I ran chat. It seems to want to use the local terminal as the modem and it does not talk to the modem. How do I specify the modem name to chat?
- 17.7 When I run pppd and chat along with mgetty then the connection does not start. If I stop mgetty, then pppd will work. Why?
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