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