Re: I can send packets but I receive nothing, routing problem

From: riviereg (
Date: 09/04/04

  • Next message: Stefan Viljoen: "Re: smbmount <==> fstab .. and a touch of "Called name not present""
    Date: Sat, 04 Sep 2004 18:04:24 +0700

    Alex Harsch wrote:
    > riviereg wrote:
    >>Dear all linux networking,
    >>I try to set up a route to my ISP:
    >>my network is connected to the router on eth0
    >>my ISP is on link eth2 on my router (GNU/Debian sarge, kernel 2.6.8, I
    >>try with 2.6.7 same problem).
    >>my external IP is
    >>my gateway is (this is my modem, with a real IP address)
    >>I try to route my internal IP to this ISP
    >>my route is configure like this:
    >># ADSL line
    >>ip route flush table 5
    >>ip route add table 5 default via src dev eth2
    >>ip rule add fwmark 5 table 5
    >>my Nat is like this
    >>iptables -t mangle -A PREROUTING -s -j MARK --set-mark 5
    >>iptables -t nat -A POSTROUTING -o eth2 -s -j SNAT --to
    >>All is ok, I can access to my modem ( from, I can also
    >>access to internet on this modem (there is a web site on the modem).
    >>But when I try to access to Internet from, I can "find" sites
    >>but I receive nothing, all my ping are lost. This problem drive me crasy
    >>I think I send packets but there is a kind of incoming reply routing
    >>problem. All other IP's from my internal network can connect with the
    >>default gateway on my first ISP (eth1).
    >>Thank you for Help me on this,
    > Bon Jour Guillaume,
    > I think, you have a couple of problems here. First of all, you default
    > gateway should not be the modem, but your interface pppx.
    > Additionally, I think you have not configured your firewall to allow
    > incoming related/acknowledged packets.

    Thank you for this Alex,

    I fact I have a modem gateway with an assigned real IP Address,

    Internal Network ----| Linux box |-----| Modem gateway |----
                                            | Computer x |

    I aslo try to connect directly a computer (x) to the Modem gateway,
    with this modem as gateway and another real IP address provided by
    my ISP. From computer X I can access to Internet, no problem

    How to configure my firewall to allow incoming related/ackowledged
    packets ? I think my problem is something like this.

    Thank you very much for help,

  • Next message: Stefan Viljoen: "Re: smbmount <==> fstab .. and a touch of "Called name not present""

    Relevant Pages

    • Connect to internal lan using PPP
      ... It's currently the default gateway for an internal lan and I'd like to ... internet cable, one internal for home and runs natd for the other local pc. ... If i delete this route on the windows client and ... # set dns ...
    • Re: One computer on 2 networks
      ... The gateway setting on the 172.30 NIC should be blank. ... If they are not all 172.30 you need to use a shorter network mask (so ... How exactly would the Route Add sentence be? ... and yours must point to the Internet gateway. ...
    • Re: home lan setup suggestions
      ... Router internet config dialog shows: ... Default gateway:, being the IP assigned by ISP ... Modem manages the connection/disconnection to internet, ... The router itself uses the gateway IP given to it by the ISP. ...
    • Re: Dual NICs on Server 2003 issue
      ... To route a particular set of addresses to some other ... gateway you need to use static routing. ... connects via another gateway to a remote site that is on a 10.0.1.x ... assuming you have two internet access? ...
    • Re: networking
      ... > Really bottom line each machine will connect to the internet and each ... > Is the modem a cable or DSL modem on either PC? ... > Modem on linux is external US Robitics 56k on XP lucent PCI win modem ... >> Read the man or XP Home for details of the route statements. ...