Linux PPP HOWTO

Al Longyear, `longyear@netcom.com`

v1.11, 12 July 1995

This 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.

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 Where should I post questions about PPP?

2.7 The PPP software doesn't work. HELP!!!

2.8 How do I use PPP with a system which uses dynamic IP assignments? It assigns a different IP address to me with each call.

2.9 How do I know what IP address was given to me when it is dynamically assigned?

2.10 Can I use the same local IP address for each line of a PPP server?

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?

5. Authentication files

5.1 What goes into the `/etc/PPP/pap-secrets` file? Do you have a sample?

5.2 What goes into the `/etc/PPP/chap-secrets` file? Do you have a sample?

6. Construction problems

6.1 I get compile errors when I try to compile the kernel

7. Problems running pppd

7.1 `pppd` wont run unless you are root

7.2 The `ppp-2.1.2d` package says it needs the 4.6 libraries

7.3 `unable to create pid file: no such file or directory`

7.4 `/etc/PPP/options: no such file or directory`

7.5 `Could not determine local IP address`

7.6 `Could not determine remote IP address`

7.7 I keep getting the message to the effect that the magic number is always NAKed. The system will not connect.

7.8 `protocol reject for protocol fffb`

7.9 The PPP software connects, sends quite a few frames, but still does not seem to connect. Why is that?

7.10 I can't connect to the merit network.

8. DIP

8.1 DIP does not have support for PPP's mode

9. Process termination

9.1 Is there a ``dip -k`' for PPP?

9.2 PPP does not hangup the modem when it terminates

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 can reach the remote server, but I can not get anywhere else.

11.3 I have a default route and I still can't get anywhere else! Now what?

11.4 I can not ping my local IP address

12. Interactions with other PPP implementations

12.1 I am using a `Trumpet` (for `MSDOS`) and the connection simply terminates. Why is this happening?

12.2 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?

12.3 I can not connect to/with my Windows NT code (originally called 'Daytona')

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 The connection fails with an `ioctl(TIOCSCTTY)` error.

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

14. Network routing issues (using PPP as a `cheap' bridge)

14.1 `Slattach` and `ifconfig` don't work like 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 How about just standard synchronous PPP?

16. Miscellenous

16.1 Do you have a PPP compatible mail reader?

16.2 How about a news reader?