PPP netmask problem - PPP

This is a discussion on PPP netmask problem - PPP ; I have successfully set up mgetty + ppp on our linux server in the past for the office to use as a dialin ISP server so they can come in on a 1-800 #, and surf out on our T-1. ...

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Thread: PPP netmask problem

  1. PPP netmask problem

    I have successfully set up mgetty + ppp on our linux server in the past
    for the office to use as a dialin ISP server so they can come in on a
    1-800 #, and surf out on our T-1. I am failing with my current setup,
    SUSE 9.3. I installed latest ppp, still failure. I can establish
    connection, but "netmask" option does not seem to be issued. Logs are
    silent about "netmask".

    Does "netmask" option still work for ppp? If so, would something else
    prevent ppp from handing out the netmask? And how can I locate it? Or
    is there another option to route traffic from modem out to the T-1?

    Thanks, Marion


  2. Re: PPP netmask problem

    marion.keith@gmail.com writes:
    > I have successfully set up mgetty + ppp on our linux server in the past
    > for the office to use as a dialin ISP server so they can come in on a
    > 1-800 #, and surf out on our T-1. I am failing with my current setup,
    > SUSE 9.3. I installed latest ppp, still failure. I can establish
    > connection, but "netmask" option does not seem to be issued. Logs are
    > silent about "netmask".
    >
    > Does "netmask" option still work for ppp? If so, would something else
    > prevent ppp from handing out the netmask? And how can I locate it? Or
    > is there another option to route traffic from modem out to the T-1?


    "Netmask" is pretty meaningless on point-to-point links. With a
    point-to-point link, there's only *one* peer any of your transmitted
    packets can go to. That's a single IP address, not a subnet, so
    there's no way to talk about a netmask in this context.

    Certain Router Vendors have added features to their boxes that allow
    you to set a netmask on point-to-point links. What that feature
    _actually_ does is establish a static route by masking off the local
    address[1] with the supplied mask and pointing the next hop of the
    generated route to the peer.

    Sadly, that's a bit misleading.

    The right way to do this is to either add static routes (you can do
    this via /etc/ppp/ip-up if you like) or just use a routing protocol.
    This (figuring out where all those links go) is what routing protocols
    were designed to do.

    [1] One major vendor uses the local address, another well-known vendor
    uses the remote address. There's no standard.

    --
    James Carlson, KISS Network
    Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

  3. Re: PPP netmask problem

    Thanks for the explanation. I should be able to apply it in ip-up.

    Has the netmask option been taken out of the Paul's PPP Package version
    2.4.3 for Linux?

    Thanks, Marion


  4. Re: PPP netmask problem

    marion.keith@gmail.com writes:
    > Thanks for the explanation. I should be able to apply it in ip-up.
    >
    > Has the netmask option been taken out of the Paul's PPP Package version
    > 2.4.3 for Linux?


    No. It looks like the code checks to see if you have kernel version
    2.1.16 or better and silently forces the mask to 255.255.255.255 if
    so.

    It's a placebo option -- parsed and accepted, but does nothing.

    --
    James Carlson, KISS Network
    Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

  5. Re: PPP netmask problem

    Thanks, James. That explains a lot that I wasn't turning up out there.
    Thanks again for the help. Marion


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