Documentation/isdn/syncPPP.FAQ

   1 simple isdn4linux PPP FAQ .. to be continued .. not 'debugged'
   2 -------------------------------------------------------------------
   3
   4 Q01: what's pppd, ipppd, syncPPP, asyncPPP ??
   5 Q02: error message "this system lacks PPP support"
   6 Q03: strange information using 'ifconfig'
   7 Q04: MPPP?? What's that and how can I use it ...
   8 Q05: I tried MPPP but it doesn't work
   9 Q06: can I use asynchronous PPP encapsulation with network devices
  10 Q07: A SunISDN machine can't connect to my i4l system
  11 Q08: I wanna talk to several machines, which need different configs
  12 Q09: Starting the ipppd, I get only error messages from i4l
  13 Q10: I wanna use dynamic IP address assignment
  14 Q11: I can't connect. How can I check where the problem is.
  15 Q12: How can I reduce login delay?
  16
  17 -------------------------------------------------------------------
  18
  19 Q01: pppd, ipppd, syncPPP, asyncPPP .. what is that ?
  20    what should I use?
  21 A: The pppd is for asynchronous PPP .. asynchronous means
  22    here, the framing is character based. (e.g when
  23    using ttyI* or tty* devices)
  24
  25    The ipppd handles PPP packets coming in HDLC
  26    frames (bit based protocol) ... The PPP driver
  27    in isdn4linux pushes all IP packets direct
  28    to the network layer and all PPP protocol
  29    frames to the /dev/ippp* device.
  30    So, the ipppd is a simple external network
  31    protocol handler.
  32
  33    If you login into a remote machine using the
  34    /dev/ttyI* devices and then enable PPP on the
  35    remote terminal server -> use the 'old' pppd
  36
  37    If your remote side immediately starts to send
  38    frames ... you probably connect to a
  39    syncPPP machine .. use the network device part
  40    of isdn4linux with the 'syncppp' encapsulation
  41    and make sure, that the ipppd is running and
  42    connected to at least one /dev/ippp*. Check the
  43    isdn4linux manual on how to configure a network device.
  44
  45 --
  46
  47 Q02: when I start the ipppd .. I only get the
  48    error message "this system lacks PPP support"
  49 A: check that at least the device 'ippp0' exists.
  50    (you can check this e.g with the program 'ifconfig')
  51    The ipppd NEEDS this device under THIS name ..
  52    If this device doesn't exists, use:
  53         isdnctrl addif ippp0
  54         isdnctrl encap ippp0 syncppp
  55         ... (see isdn4linux doc for more) ...
  56 A: Maybe you have compiled the ipppd with another
  57    kernel source tree than the kernel you currently
  58    run ...
  59
  60 --
  61
  62 Q03: when I list the netdevices with ifconfig I see, that
  63    my ISDN interface has a HWaddr and IRQ=0 and Base
  64    address = 0
  65 A: The device is a fake ethernet device .. ignore IRQ and baseaddr
  66    You need the HWaddr only for ethernet encapsulation.
  67
  68 --
  69
  70 Q04: MPPP?? What's that and how can I use it ...
  71
  72 A: MPPP or MP or MPP (Warning: MP is also an
  73    acronym for 'Multi Processor') stands for
  74    Multi Point to Point and means bundling
  75    of several channels to one logical stream.
  76    To enable MPPP negotiation you must call the
  77    ipppd with the '+mp' option.
  78    You must also configure a slave device for
  79    every additional channel. (see the i4l manual
  80    for more)
  81    To use channel bundling you must first activate
  82    the 'master' or initial call. Now you can add
  83    the slave channels with the command:
  84        isdnctrl addlink <device>
  85    e.g:
  86        isdnctrl addlink ippp0
  87    This is different from other encapsulations of
  88    isdn4linux! With syncPPP, there is no automatic
  89    activation of slave devices.
  90
  91 --
  92
  93 Q05: I tried MPPP but it doesn't work .. the ipppd
  94    writes in the debug log something like:
  95    .. rcvd [0][proto=0x3d] c0 00 00 00 80 fd 01 01 00 0a ...
  96    .. sent [0][LCP ProtRej id=0x2 00 3d c0 00 00 00 80 fd 01 ...
  97
  98 A: you forgot to compile MPPP/RFC1717 support into the
  99    ISDN Subsystem. Recompile with this option enabled.
 100
 101 --
 102
 103 Q06: can I use asynchronous PPP encapsulation
 104    over the network interface of isdn4linux ..
 105
 106 A: No .. that's not possible .. Use the standard
 107    PPP package over the /dev/ttyI* devices. You
 108    must not use the ipppd for this.
 109
 110 --
 111
 112 Q07: A SunISDN machine tries to connect my i4l system,
 113    which doesn't work.
 114    Checking the debug log I just saw garbage like:
 115 !![ ... fill in the line ... ]!!
 116
 117 A: The Sun tries to talk asynchronous PPP ... i4l
 118    can't understand this ... try to use the ttyI*
 119    devices with the standard PPP/pppd package
 120
 121 A: (from Alexanter Strauss: )
 122 !![ ... fill in mail ]!!
 123
 124 --
 125
 126 Q08: I wanna talk to remote machines, which need
 127    a different configuration. The only way
 128    I found to do this is to kill the ipppd and
 129    start a new one with another config to connect
 130    to the second machine.
 131
 132 A: you must bind a network interface explicitly to
 133    an ippp device, where you can connect a (for this
 134    interface) individually configured ipppd.
 135
 136 --
 137
 138 Q09: When I start the ipppd I only get error messages
 139    from the i4l driver ..
 140
 141 A: When starting, the ipppd calls functions which may
 142    trigger a network packet. (e.g gethostbyname()).
 143    Without the ipppd (at this moment, it is not
 144    fully started) we can't handle this network request.
 145    Try to configure hostnames necessary for the ipppd
 146    in your local /etc/hosts file or in a way, that
 147    your system can resolve it without using an
 148    isdn/ippp network-interface.
 149
 150 --
 151
 152 Q10: I wanna use dynamic IP address assignment ... How
 153    must I configure the network device.
 154
 155 A: At least you must have a route which forwards
 156    a packet to the ippp network-interface to trigger
 157    the dial-on-demand.
 158    A default route to the ippp-interface will work.
 159    Now you must choose a dummy IP address for your
 160    interface.
 161    If for some reason you can't set the default
 162    route to the ippp interface, you may take any
 163    address of the subnet from which you expect your
 164    dynamic IP number and set a 'network route' for
 165    this subnet to the ippp interface.
 166    To allow overriding of the dummy address you
 167    must call the ipppd with the 'ipcp-accept-local' option.
 168
 169 A: You must know, how the ipppd gets the addresses it wanna
 170    configure. If you don't give any option, the ipppd
 171    tries to negotiate the local host address!
 172    With the option 'noipdefault' it requests an address
 173    from the remote machine. With 'useifip' it gets the
 174    addresses from the net interface. Or you set the address
 175    on the option line with the <a.b.c.d:e.f.g.h> option.
 176    Note: the IP address of the remote machine must be configured
 177    locally or the remote machine must send it in an IPCP request.
 178    If your side doesn't know the IP address after negotiation, it
 179    closes the connection!
 180    You must allow overriding of address with the 'ipcp-accept-*'
 181    options, if you have set your own or the remote address
 182    explicitly.
 183
 184 A: Maybe you try these options .. e.g:
 185
 186     /sbin/ipppd :$REMOTE noipdefault /dev/ippp0
 187
 188    where REMOTE must be the address of the remote machine (the
 189    machine, which gives you your address)
 190
 191 --
 192
 193 Q11: I can't connect. How can I check where the problem is.
 194
 195 A: A good help log is the debug output from the ipppd...
 196    Check whether you can find there:
 197    - only a few LCP-conf-req SENT messages (less then 10)
 198      and then a Term-REQ:
 199      -> check whether your ISDN card is well configured
 200         it seems, that your machine doesn't dial
 201         (IRQ,IO,Proto, etc problems)
 202         Configure your ISDN card to print debug messages and
 203         check the /dev/isdnctrl output next time. There
 204         you can see, whether there is activity on the card/line.
 205    - there are at least a few RECV messages in the log:
 206      -> fine: your card is dialing and your remote machine
 207         tries to talk with you. Maybe only a missing
 208         authentication. Check your ipppd configuration again.
 209    - the ipppd exits for some reason:
 210      -> not good ... check /var/adm/syslog and /var/adm/daemon.
 211         Could be a bug in the ipppd.
 212
 213 --
 214
 215 Q12: How can I reduce login delay?
 216
 217 A: Log a login session ('debug' log) and check which options
 218   your remote side rejects. Next time configure your ipppd
 219   to not negotiate these options. Another 'side effect' is, that
 220   this increases redundancy. (e.g your remote side is buggy and
 221   rejects options in a wrong way).
 222
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