PPP randomly dials out - PPP

This is a discussion on PPP randomly dials out - PPP ; I am running PPP on a linux redhat 7.2 kernel to demand dial to some PC's out in the field. Occasionally my modem starts dialing and connects to a PC without any traffic being started for that IP. Is there ...

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  1. PPP randomly dials out

    I am running PPP on a linux redhat 7.2 kernel to demand dial to some
    PC's out in the field. Occasionally my modem starts dialing and
    connects to a PC without any traffic being started for that IP. Is
    there something that would cause it to dial out and connect. The link
    seems to connect as if some broadcast traffic is starting the link.
    Demand dialing is setup to disconnect with the idle command and the
    modem ends up connecting and then going dormant and disconnecting.
    This is happening several times throught a normal day. This concerns
    me about the PPP stability.

  2. Re: PPP randomly dials out

    dirtytoyota@hotmail.com (PullnOutHair) writes:

    ]I am running PPP on a linux redhat 7.2 kernel to demand dial to some
    ]PC's out in the field. Occasionally my modem starts dialing and
    ]connects to a PC without any traffic being started for that IP. Is

    No, you mean without you starting traffic. There almost certainly is
    some traffic that is triggering the modem. Also it would help if you
    told us your setup. Demand dialing is not to "some PCs' It is to a very
    specific one. And it does this whenever ANY traffic needs to be sent to
    whatever IP address.

    ]there something that would cause it to dial out and connect. The link
    ]seems to connect as if some broadcast traffic is starting the link.

    Could be.

    ]Demand dialing is setup to disconnect with the idle command and the
    ]modem ends up connecting and then going dormant and disconnecting.
    ]This is happening several times throught a normal day. This concerns
    ]me about the PPP stability.

    ppp stability is fine.

  3. Re: PPP randomly dials out

    unruh@string.physics.ubc.ca (Bill Unruh) wrote in message news:...
    > dirtytoyota@hotmail.com (PullnOutHair) writes:
    >
    > ]I am running PPP on a linux redhat 7.2 kernel to demand dial to some
    > ]PC's out in the field. Occasionally my modem starts dialing and
    > ]connects to a PC without any traffic being started for that IP. Is
    >
    > No, you mean without you starting traffic. There almost certainly is
    > some traffic that is triggering the modem. Also it would help if you
    > told us your setup. Demand dialing is not to "some PCs' It is to a very
    > specific one. And it does this whenever ANY traffic needs to be sent to
    > whatever IP address.


    Actually, I am using ppp demand dialing to connect to 4 different PC's
    right now. I have a function that replaces the call number dependent
    upon which PC the traffic is for. Because of this I am not sure, nor
    do the ppp debug logs show, which PC the traffic is for. I would love
    it if I could set up demand dialing so that I could get rid of the
    function and use strictly IP address to determine which number to
    call. Currently, I have had to build that in and let all 4 PC's use
    the same IP.

    My setup is very basic since I am just starting out. I have PPP
    configured for dial on demand, and also for dial-in as a server using
    mgetty. I have the linux box acting as a server/firewall that uses
    NAT to hide the subnet of the PPP machines that connect to it. My LAN
    has a subnet of 10.0.0.x and the PPP is setup to have a subnet of
    192.168.0.x. There shouldn't be any traffic that is generated outside
    of the PPP network that can trigger a dial since the subnets won't
    match up. The only machines on the PPP end are my linux box (PPP
    server and demand dialer) and the PC that is on the other end that it
    connects to. The problem is that all the machines that it connects to
    use cellular modems and this random dialing eats up 2 minutes of
    airtime everytime it happens because of the idle setting. I can't
    lower this setting due to other program constraints. Anything that
    you think would be helpful let me know. I am very glad to post
    anything that may help you help me.

    Thank you for all the past and future help.



    >
    > ]there something that would cause it to dial out and connect. The link
    > ]seems to connect as if some broadcast traffic is starting the link.
    >
    > Could be.
    >
    > ]Demand dialing is setup to disconnect with the idle command and the
    > ]modem ends up connecting and then going dormant and disconnecting.
    > ]This is happening several times throught a normal day. This concerns
    > ]me about the PPP stability.
    >
    > ppp stability is fine.


  4. Re: PPP randomly dials out

    dirtytoyota@hotmail.com (PullnOutHair) writes:

    ]unruh@string.physics.ubc.ca (Bill Unruh) wrote in message news:...
    ]> dirtytoyota@hotmail.com (PullnOutHair) writes:
    ]>
    ]> ]I am running PPP on a linux redhat 7.2 kernel to demand dial to some
    ]> ]PC's out in the field. Occasionally my modem starts dialing and
    ]> ]connects to a PC without any traffic being started for that IP. Is
    ]>
    ]> No, you mean without you starting traffic. There almost certainly is
    ]> some traffic that is triggering the modem. Also it would help if you
    ]> told us your setup. Demand dialing is not to "some PCs' It is to a very
    ]> specific one. And it does this whenever ANY traffic needs to be sent to
    ]> whatever IP address.

    ]Actually, I am using ppp demand dialing to connect to 4 different PC's
    ]right now. I have a function that replaces the call number dependent
    ]upon which PC the traffic is for. Because of this I am not sure, nor

    OK, you have a non-standard useage of ppp demand dialing. Not surprising
    that you might have some issues.
    Note that they might be some sort of broadcast packets, or arp requests
    that are getting sent out. Can you use tcpdump to see what the traffic
    is? (Not sure if there is any device to attack tcpdump to when it is
    down under demand dialing however).


    ]do the ppp debug logs show, which PC the traffic is for. I would love
    ]it if I could set up demand dialing so that I could get rid of the
    ]function and use strictly IP address to determine which number to
    ]call. Currently, I have had to build that in and let all 4 PC's use
    ]the same IP.

    The packet is almost certainly for the IP address, not for some specific
    PC.



    ]My setup is very basic since I am just starting out. I have PPP
    ]configured for dial on demand, and also for dial-in as a server using
    ]mgetty. I have the linux box acting as a server/firewall that uses
    ]NAT to hide the subnet of the PPP machines that connect to it. My LAN
    ]has a subnet of 10.0.0.x and the PPP is setup to have a subnet of
    ]192.168.0.x. There shouldn't be any traffic that is generated outside
    ]of the PPP network that can trigger a dial since the subnets won't
    ]match up. The only machines on the PPP end are my linux box (PPP

    A broadcast packet matches everything.


    ]server and demand dialer) and the PC that is on the other end that it
    ]connects to. The problem is that all the machines that it connects to
    ]use cellular modems and this random dialing eats up 2 minutes of
    ]airtime everytime it happens because of the idle setting. I can't
    ]lower this setting due to other program constraints. Anything that
    ]you think would be helpful let me know. I am very glad to post
    ]anything that may help you help me.

    I am not sure I can be of further help, since I do not know demand
    dialing well at all.

    You might want to look into diald, the old program for doing demand
    dialing. I think it had a packet filter option which could be used to
    restrict the types of packets which would trigger the dialout.
    But you still need to find out what is triggering it. Are there regular
    times that this is happening?



    ]Thank you for all the past and future help.
    ]


    ]>
    ]> ]there something that would cause it to dial out and connect. The link
    ]> ]seems to connect as if some broadcast traffic is starting the link.
    ]>
    ]> Could be.
    ]>
    ]> ]Demand dialing is setup to disconnect with the idle command and the
    ]> ]modem ends up connecting and then going dormant and disconnecting.
    ]> ]This is happening several times throught a normal day. This concerns
    ]> ]me about the PPP stability.
    ]>
    ]> ppp stability is fine.


  5. Re: PPP randomly dials out

    dirtytoyota@hotmail.com (PullnOutHair) writes:
    > I am running PPP on a linux redhat 7.2 kernel to demand dial to some
    > PC's out in the field. Occasionally my modem starts dialing and
    > connects to a PC without any traffic being started for that IP.


    That doesn't sound likely.

    However, assuming you've got a recent version of pppd (you didn't
    say), a reasonable thing to do would be to look at the debug logs --
    the first packet sent after bringing the link up should be the
    culprit. If that's not doable for some reason, then instrumenting
    ip_active_pkt() in ipcp.c should reveal what's triggering the dial
    (assuming it's IPv4 activity).

    > Is
    > there something that would cause it to dial out and connect. The link
    > seems to connect as if some broadcast traffic is starting the link.


    Broadcast traffic is not forwarded by the Linux kernel, at least by
    default. Even if it were forwarded, this wouldn't be a problem in PPP
    itself -- it'd just be doing what was asked. The real problem (if
    there were such a problem) would be in the kernel itself.

    > Demand dialing is setup to disconnect with the idle command and the
    > modem ends up connecting and then going dormant and disconnecting.
    > This is happening several times throught a normal day. This concerns
    > me about the PPP stability.


    It shouldn't.

    --
    James Carlson, IP Systems Group
    Sun Microsystems / 1 Network Drive 71.234W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.497N Fax +1 781 442 1677

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