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
223
224
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