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+simple isdn4linux PPP FAQ .. to be continued .. not 'debugged'
+-------------------------------------------------------------------
+
+Q01: what's pppd, ipppd, syncPPP, asyncPPP ??
+Q02: error message "this system lacks PPP support"
+Q03: strange information using 'ifconfig'
+Q04: MPPP?? What's that and how can I use it ...
+Q05: I tried MPPP but it doesn't work
+Q06: can I use asynchronous PPP encapsulation with network devices
+Q07: A SunISDN machine can't connect to my i4l system
+Q08: I wanna talk to several machines, which need different configs
+Q09: Starting the ipppd, I get only error messages from i4l
+Q10: I wanna use dynamic IP address assignment
+Q11: I can't connect. How can I check where the problem is.
+Q12: How can I reduce login delay?
+
+-------------------------------------------------------------------
+
+Q01: pppd, ipppd, syncPPP, asyncPPP .. what is that ?
+ what should I use?
+A: The pppd is for asynchronous PPP .. asynchronous means
+ here, the framing is character based. (e.g when
+ using ttyI* or tty* devices)
+
+ The ipppd handles PPP packets coming in HDLC
+ frames (bit based protocol) ... The PPP driver
+ in isdn4linux pushes all IP packets direct
+ to the network layer and all PPP protocol
+ frames to the /dev/ippp* device.
+ So, the ipppd is a simple external network
+ protocol handler.
+
+ If you login into a remote machine using the
+ /dev/ttyI* devices and then enable PPP on the
+ remote terminal server -> use the 'old' pppd
+
+ If your remote side immediately starts to send
+ frames ... you probably connect to a
+ syncPPP machine .. use the network device part
+ of isdn4linux with the 'syncppp' encapsulation
+ and make sure, that the ipppd is running and
+ connected to at least one /dev/ippp*. Check the
+ isdn4linux manual on how to configure a network device.
+
+--
+
+Q02: when I start the ipppd .. I only get the
+ error message "this system lacks PPP support"
+A: check that at least the device 'ippp0' exists.
+ (you can check this e.g with the program 'ifconfig')
+ The ipppd NEEDS this device under THIS name ..
+ If this device doesn't exists, use:
+ isdnctrl addif ippp0
+ isdnctrl encap ippp0 syncppp
+ ... (see isdn4linux doc for more) ...
+A: Maybe you have compiled the ipppd with another
+ kernel source tree than the kernel you currently
+ run ...
+
+--
+
+Q03: when I list the netdevices with ifconfig I see, that
+ my ISDN interface has a HWaddr and IRQ=0 and Base
+ address = 0
+A: The device is a fake ethernet device .. ignore IRQ and baseaddr
+ You need the HWaddr only for ethernet encapsulation.
+
+--
+
+Q04: MPPP?? What's that and how can I use it ...
+
+A: MPPP or MP or MPP (Warning: MP is also an
+ acronym for 'Multi Processor') stands for
+ Multi Point to Point and means bundling
+ of several channels to one logical stream.
+ To enable MPPP negotiation you must call the
+ ipppd with the '+mp' option.
+ You must also configure a slave device for
+ every additional channel. (see the i4l manual
+ for more)
+ To use channel bundling you must first activate
+ the 'master' or initial call. Now you can add
+ the slave channels with the command:
+ isdnctrl addlink <device>
+ e.g:
+ isdnctrl addlink ippp0
+ This is different from other encapsulations of
+ isdn4linux! With syncPPP, there is no automatic
+ activation of slave devices.
+
+--
+
+Q05: I tried MPPP but it doesn't work .. the ipppd
+ writes in the debug log something like:
+ .. rcvd [0][proto=0x3d] c0 00 00 00 80 fd 01 01 00 0a ...
+ .. sent [0][LCP ProtRej id=0x2 00 3d c0 00 00 00 80 fd 01 ...
+
+A: you forgot to compile MPPP/RFC1717 support into the
+ ISDN Subsystem. Recompile with this option enabled.
+
+--
+
+Q06: can I use asynchronous PPP encapsulation
+ over the network interface of isdn4linux ..
+
+A: No .. that's not possible .. Use the standard
+ PPP package over the /dev/ttyI* devices. You
+ must not use the ipppd for this.
+
+--
+
+Q07: A SunISDN machine tries to connect my i4l system,
+ which doesn't work.
+ Checking the debug log I just saw garbage like:
+!![ ... fill in the line ... ]!!
+
+A: The Sun tries to talk asynchronous PPP ... i4l
+ can't understand this ... try to use the ttyI*
+ devices with the standard PPP/pppd package
+
+A: (from Alexanter Strauss: )
+!![ ... fill in mail ]!!
+
+--
+
+Q08: I wanna talk to remote machines, which need
+ a different configuration. The only way
+ I found to do this is to kill the ipppd and
+ start a new one with another config to connect
+ to the second machine.
+
+A: you must bind a network interface explicitly to
+ an ippp device, where you can connect a (for this
+ interface) individually configured ipppd.
+
+--
+
+Q09: When I start the ipppd I only get error messages
+ from the i4l driver ..
+
+A: When starting, the ipppd calls functions which may
+ trigger a network packet. (e.g gethostbyname()).
+ Without the ipppd (at this moment, it is not
+ fully started) we can't handle this network request.
+ Try to configure hostnames necessary for the ipppd
+ in your local /etc/hosts file or in a way, that
+ your system can resolve it without using an
+ isdn/ippp network-interface.
+
+--
+
+Q10: I wanna use dynamic IP address assignment ... How
+ must I configure the network device.
+
+A: At least you must have a route which forwards
+ a packet to the ippp network-interface to trigger
+ the dial-on-demand.
+ A default route to the ippp-interface will work.
+ Now you must choose a dummy IP address for your
+ interface.
+ If for some reason you can't set the default
+ route to the ippp interface, you may take any
+ address of the subnet from which you expect your
+ dynamic IP number and set a 'network route' for
+ this subnet to the ippp interface.
+ To allow overriding of the dummy address you
+ must call the ipppd with the 'ipcp-accept-local' option.
+
+A: You must know, how the ipppd gets the addresses it wanna
+ configure. If you don't give any option, the ipppd
+ tries to negotiate the local host address!
+ With the option 'noipdefault' it requests an address
+ from the remote machine. With 'useifip' it gets the
+ addresses from the net interface. Or you set the address
+ on the option line with the <a.b.c.d:e.f.g.h> option.
+ Note: the IP address of the remote machine must be configured
+ locally or the remote machine must send it in an IPCP request.
+ If your side doesn't know the IP address after negotiation, it
+ closes the connection!
+ You must allow overriding of address with the 'ipcp-accept-*'
+ options, if you have set your own or the remote address
+ explicitly.
+
+A: Maybe you try these options .. e.g:
+
+ /sbin/ipppd :$REMOTE noipdefault /dev/ippp0
+
+ where REMOTE must be the address of the remote machine (the
+ machine, which gives you your address)
+
+--
+
+Q11: I can't connect. How can I check where the problem is.
+
+A: A good help log is the debug output from the ipppd...
+ Check whether you can find there:
+ - only a few LCP-conf-req SENT messages (less then 10)
+ and then a Term-REQ:
+ -> check whether your ISDN card is well configured
+ it seems, that your machine doesn't dial
+ (IRQ,IO,Proto, etc problems)
+ Configure your ISDN card to print debug messages and
+ check the /dev/isdnctrl output next time. There
+ you can see, whether there is activity on the card/line.
+ - there are at least a few RECV messages in the log:
+ -> fine: your card is dialing and your remote machine
+ tries to talk with you. Maybe only a missing
+ authentication. Check your ipppd configuration again.
+ - the ipppd exits for some reason:
+ -> not good ... check /var/adm/syslog and /var/adm/daemon.
+ Could be a bug in the ipppd.
+
+--
+
+Q12: How can I reduce login delay?
+
+A: Log a login session ('debug' log) and check which options
+ your remote side rejects. Next time configure your ipppd
+ to not negotiate these options. Another 'side effect' is, that
+ this increases redundancy. (e.g your remote side is buggy and
+ rejects options in a wrong way).
+
+
+