Linux PPP Null Modem Connection - PPP

This is a discussion on Linux PPP Null Modem Connection - PPP ; Dear all, Please could you help me to establish PPP connection between 2 Linux boxes enabling the client to go to Internet through a serial cable and the server? On both of the machines there is a fresh Mandriva 2008.1 ...

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Thread: Linux PPP Null Modem Connection

  1. Linux PPP Null Modem Connection

    Dear all,

    Please could you help me to establish PPP connection between 2 Linux
    boxes enabling the client to go to Internet through a serial cable and
    the server?
    On both of the machines there is a fresh Mandriva 2008.1 installation
    with all updates available.
    One of the machines (server) is a part of a local area network and is
    connected to the Internet via Ethernet.
    The other machine (client) is only connected via serial cable to
    server.
    What I want to do is to be able to connect to Internet from the client
    machine via serial cable connected to server. Firstly I would like to
    be able to ping any Interned address from client.

    I have disabled firewall and then I have enabled IP forwarding - I
    have set net.ipv4.ip_forward = 1 in
    /etc/sysctl.conf.
    Then I followed chapter 29 "Using PPP across a null modem (direct
    serial) connection" of http://tldp.org/HOWTO/PPP-HOWTO/ and in
    addition to I have disabled authentication and compression in the
    options files to make first try as easy as possible.

    /etc/ppp/options.ttyS1 on server is:
    crtscts
    lock
    192.168.1.1:192.168.1.2
    debug
    proxyarp
    noauth
    nodeflate
    nobsdcomp

    /etc/ppp/options.ttyS1 on client is:
    crtscts
    lock
    defaultroute
    192.168.1.2:192.168.1.1
    debug
    noauth
    nodeflate
    nobsdcomp

    I have called “pppd /dev/ttyS1” nodetach firstly on server and then
    on client.
    The result on server was:
    pppd nodetach /dev/ttyS1
    using channel 1
    Using interface ppp0
    Connect: ppp0 <--> /dev/ttyS1
    sent [LCP ConfReq id=0x1
    ]
    rcvd [LCP ConfAck id=0x1
    ]
    rcvd [LCP ConfReq id=0x1
    ]
    sent [LCP ConfAck id=0x1
    ]
    sent [IPCP ConfReq id=0x1
    ]
    rcvd [IPCP ConfReq id=0x1 dns1 0.0.0.0> ]
    sent [IPCP ConfRej id=0x1 ]
    rcvd [IPCP ConfRej id=0x1 ]
    sent [IPCP ConfReq id=0x2 ]
    rcvd [IPCP ConfReq id=0x2 ]
    sent [IPCP ConfAck id=0x2 ]
    rcvd [IPCP ConfAck id=0x2 ]
    Cannot determine ethernet address for proxy ARP
    local* IP address 192.168.1.1
    remote IP address 192.168.1.2

    the result on client was:
    pppd nodetach /dev/ttyS1
    using channel 1
    Using interface ppp0
    Connect: ppp0 <--> /dev/ttyS1
    sent [LCP ConfReq id=0x1
    ]
    rcvd [LCP ConfAck id=0x1
    ]
    rcvd [LCP ConfReq id=0x1
    ]
    sent [LCP ConfAck id=0x1
    ]
    sent [IPCP ConfReq id=0x1 dns1 0.0.0.0> ]
    rcvd [IPCP ConfReq id=0x1
    sent [IPCP ConfRej id=0x1 ]
    rcvd [IPCP ConfRej id=0x1 ]
    sent [IPCP ConfReq id=0x2 ]
    rcvd [IPCP ConfReq id=0x2 ]
    sent [IPCP ConfAck id=0x2 ]
    rcvd [IPCP ConfAck id=0x2 ]
    local* IP address 192.168.1.2
    remote IP address 192.168.1.1

    After the connection was established I could ping 192.168.1.1. from
    the client
    and 192.168.1.2 from the server. But was not able to ping any other
    address
    and could not go to the Internet from client.

    Probably the message on server:
    Cannot determine ethernet address for proxy ARP
    which I have received might describe the problem?

    Thanks for any help
    pavel


  2. Re: Linux PPP Null Modem Connection

    pavelv writes:
    > rcvd [IPCP ConfReq id=0x2 ]
    > sent [IPCP ConfAck id=0x2 ]
    > rcvd [IPCP ConfAck id=0x2 ]
    > Cannot determine ethernet address for proxy ARP
    > local* IP address 192.168.1.1
    > remote IP address 192.168.1.2


    Those log messages look highly unlikely to me. They show the daemon
    negotiating one set of addresses and then using a completely different
    set.

    How did you capture these logs and post them? Did you paste them
    together from different files?

    > After the connection was established I could ping 192.168.1.1. from
    > the client
    > and 192.168.1.2 from the server.


    It sounds like the PPP link itself works.

    > But was not able to ping any other
    > address
    > and could not go to the Internet from client.


    That's because you have non-routable addresses. If you don't have
    multiple routable IP addresses from your ISP, then you're going to
    need to set up a NAT somewhere.

    > Probably the message on server:
    > Cannot determine ethernet address for proxy ARP
    > which I have received might describe the problem?


    No. That describes a relatively minor misconfiguration on the server
    side. You specified "proxyarp" for the server configuration, but the
    address of the client (192.168.1.2) is not in the same subnet as any
    broadcast-type (Ethernet) interface that you have configured. There's
    thus no way to do proxy ARP for that address.

    If you want proxy ARP for 192.168.1.2 to work, you'll need to have an
    appropriate 192.168.x.x network set up.

    The reason you can't get to the Internet, though, is the lack of a
    configured NAT.

    --
    James Carlson, Solaris Networking
    Sun Microsystems / 35 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: Linux PPP Null Modem Connection

    Thanks a lot James.

    Now I use only one set of IP addresses and it works. I can do to the
    Internet via serial cable and PPP.

    Thanks again,

    Pavel

  4. Re: Linux PPP Null Modem Connection


    "pavelv" wrote in message
    news:50176ad6-f861-4e41-b7d0-92d2e4a0888d@8g2000hse.googlegroups.com...
    Dear all,

    Please could you help me to establish PPP connection between 2 Linux
    boxes enabling the client to go to Internet through a serial cable and
    the server?
    On both of the machines there is a fresh Mandriva 2008.1 installation
    with all updates available.
    One of the machines (server) is a part of a local area network and is
    connected to the Internet via Ethernet.
    The other machine (client) is only connected via serial cable to
    server.
    What I want to do is to be able to connect to Internet from the client
    machine via serial cable connected to server. Firstly I would like to
    be able to ping any Interned address from client.

    I have disabled firewall and then I have enabled IP forwarding - I
    have set net.ipv4.ip_forward = 1 in
    /etc/sysctl.conf.
    Then I followed chapter 29 "Using PPP across a null modem (direct
    serial) connection" of http://tldp.org/HOWTO/PPP-HOWTO/ and in
    addition to I have disabled authentication and compression in the
    options files to make first try as easy as possible.

    /etc/ppp/options.ttyS1 on server is:
    crtscts
    lock
    192.168.1.1:192.168.1.2
    debug
    proxyarp
    noauth
    nodeflate
    nobsdcomp

    /etc/ppp/options.ttyS1 on client is:
    crtscts
    lock
    defaultroute
    192.168.1.2:192.168.1.1
    debug
    noauth
    nodeflate
    nobsdcomp

    I have called “pppd /dev/ttyS1” nodetach firstly on server and then
    on client.
    The result on server was:
    pppd nodetach /dev/ttyS1
    using channel 1
    Using interface ppp0
    Connect: ppp0 <--> /dev/ttyS1
    sent [LCP ConfReq id=0x1
    ]
    rcvd [LCP ConfAck id=0x1
    ]
    rcvd [LCP ConfReq id=0x1
    ]
    sent [LCP ConfAck id=0x1
    ]
    sent [IPCP ConfReq id=0x1
    ]
    rcvd [IPCP ConfReq id=0x1 dns1 0.0.0.0> ]
    sent [IPCP ConfRej id=0x1 ]
    rcvd [IPCP ConfRej id=0x1 ]
    sent [IPCP ConfReq id=0x2 ]
    rcvd [IPCP ConfReq id=0x2 ]
    sent [IPCP ConfAck id=0x2 ]
    rcvd [IPCP ConfAck id=0x2 ]
    Cannot determine ethernet address for proxy ARP
    local IP address 192.168.1.1
    remote IP address 192.168.1.2

    the result on client was:
    pppd nodetach /dev/ttyS1
    using channel 1
    Using interface ppp0
    Connect: ppp0 <--> /dev/ttyS1
    sent [LCP ConfReq id=0x1
    ]
    rcvd [LCP ConfAck id=0x1
    ]
    rcvd [LCP ConfReq id=0x1
    ]
    sent [LCP ConfAck id=0x1
    ]
    sent [IPCP ConfReq id=0x1 dns1 0.0.0.0> ]
    rcvd [IPCP ConfReq id=0x1
    sent [IPCP ConfRej id=0x1 ]
    rcvd [IPCP ConfRej id=0x1 ]
    sent [IPCP ConfReq id=0x2 ]
    rcvd [IPCP ConfReq id=0x2 ]
    sent [IPCP ConfAck id=0x2 ]
    rcvd [IPCP ConfAck id=0x2 ]
    local IP address 192.168.1.2
    remote IP address 192.168.1.1

    After the connection was established I could ping 192.168.1.1. from
    the client
    and 192.168.1.2 from the server. But was not able to ping any other
    address
    and could not go to the Internet from client.

    Probably the message on server:
    Cannot determine ethernet address for proxy ARP
    which I have received might describe the problem?

    Thanks for any help
    pavel



  5. Re: Linux PPP Null Modem Connection

    "rene" writes:


    >"pavelv" wrote in message
    >news:50176ad6-f861-4e41-b7d0-92d2e4a0888d@8g2000hse.googlegroups.com...
    >Dear all,


    >Please could you help me to establish PPP connection between 2 Linux
    >boxes enabling the client to go to Internet through a serial cable and
    >the server?
    >On both of the machines there is a fresh Mandriva 2008.1 installation
    >with all updates available.
    >One of the machines (server) is a part of a local area network and is
    >connected to the Internet via Ethernet.
    >The other machine (client) is only connected via serial cable to
    >server.
    >What I want to do is to be able to connect to Internet from the client
    >machine via serial cable connected to server. Firstly I would like to
    >be able to ping any Interned address from client.


    >I have disabled firewall and then I have enabled IP forwarding - I
    >have set net.ipv4.ip_forward = 1 in
    >/etc/sysctl.conf.
    >Then I followed chapter 29 "Using PPP across a null modem (direct
    >serial) connection" of http://tldp.org/HOWTO/PPP-HOWTO/ and in
    >addition to I have disabled authentication and compression in the
    >options files to make first try as easy as possible.


    >/etc/ppp/options.ttyS1 on server is:
    >crtscts
    >lock
    >192.168.1.1:192.168.1.2
    >debug
    >proxyarp
    >noauth
    >nodeflate
    >nobsdcomp


    >/etc/ppp/options.ttyS1 on client is:
    >crtscts
    >lock
    >defaultroute
    >192.168.1.2:192.168.1.1
    >debug
    >noauth
    >nodeflate
    >nobsdcomp


    >I have called “pppd /dev/ttyS1” nodetach firstly on server and then
    >on client.
    >The result on server was:
    >pppd nodetach /dev/ttyS1
    >using channel 1
    >Using interface ppp0
    >Connect: ppp0 <--> /dev/ttyS1
    >sent [LCP ConfReq id=0x1
    >]
    >rcvd [LCP ConfAck id=0x1
    >]
    >rcvd [LCP ConfReq id=0x1
    >]
    >sent [LCP ConfAck id=0x1
    >]
    >sent [IPCP ConfReq id=0x1
    > ]
    >rcvd [IPCP ConfReq id=0x1 >dns1 0.0.0.0> ]
    >sent [IPCP ConfRej id=0x1 ]
    >rcvd [IPCP ConfRej id=0x1 ]
    >sent [IPCP ConfReq id=0x2 ]
    >rcvd [IPCP ConfReq id=0x2 ]
    >sent [IPCP ConfAck id=0x2 ]
    >rcvd [IPCP ConfAck id=0x2 ]
    >Cannot determine ethernet address for proxy ARP
    >local IP address 192.168.1.1
    >remote IP address 192.168.1.2


    >the result on client was:
    >pppd nodetach /dev/ttyS1
    >using channel 1
    >Using interface ppp0
    >Connect: ppp0 <--> /dev/ttyS1
    >sent [LCP ConfReq id=0x1
    >]
    >rcvd [LCP ConfAck id=0x1
    >]
    >rcvd [LCP ConfReq id=0x1
    >]
    >sent [LCP ConfAck id=0x1
    >]
    >sent [IPCP ConfReq id=0x1 >dns1 0.0.0.0> ]
    >rcvd [IPCP ConfReq id=0x1
    > >sent [IPCP ConfRej id=0x1 ]
    >rcvd [IPCP ConfRej id=0x1 ]
    >sent [IPCP ConfReq id=0x2 ]
    >rcvd [IPCP ConfReq id=0x2 ]
    >sent [IPCP ConfAck id=0x2 ]
    >rcvd [IPCP ConfAck id=0x2 ]
    >local IP address 192.168.1.2
    >remote IP address 192.168.1.1


    >After the connection was established I could ping 192.168.1.1. from
    >the client
    >and 192.168.1.2 from the server. But was not able to ping any other
    >address
    >and could not go to the Internet from client.


    >Probably the message on server:
    >Cannot determine ethernet address for proxy ARP
    >which I have received might describe the problem?


    >Thanks for any help
    >pavel


    ppp is point to point. There is no server/client model. It connects two
    machines together. Your two machines are connected together. Now things
    have to be done via route, proxyarp, etc.

    proxyarp says that when someone asks on the "server" side for the location
    of the "client", the server will respond with its own mac address. But,
    there is no network. What you need on the "server" side is that
    masquarading be established on that side ( using your firewall software--
    usually shorewall on Linux.)
    So, I suspect that the problem is with your firewall.
    Eg, if eth0 is the ethernet connection with teh network, you need something
    like
    eth0 192.168.0.0/255.255.255.0
    in /etc/shorewall/masq
    or I think
    eth0 ppp0




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