| 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). | |