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Thread: Strange network connection.

  1. #1
    Join Date
    Jun 2006
    Location
    USA
    Beans
    151
    Distro
    Kubuntu 12.04 Precise Pangolin

    Strange network connection.

    Greetings,

    Recently I was checking out Hardinfo 0.5c and noticed that there were some ip connections listed as ESTABLISHED when I had no browser or other internet software active afaik.

    I decided that since I knew not how to flush those connections to bring down eth0, my wired connection and only connection for this box. So I did:

    Code:
    sudo ifdown eth0
    then
    Code:
    sudo ifup eth0
    My connection is static setup in /etc/network/interfaces. The interface took a short while to return to the prompt. I do an:

    Code:
    ifconfig eth0
    shows the system is up. However, when I ping my router, I get a 100% loss. I tried:

    Code:
    sudo /etc/init.d/networking restart/force-reload/stop/start
    all the available of above to try and reset the connection and bring up the network. No go.

    I then tried:
    Code:
    arp
    It returned my routers ip address and I noticed something funny no mac address. So I just rebooted the machine and normal operation returned. I ran arp again and this is what was returned:


    Code:
    [myuser@mydesktop ~]$arp
    Address                  HWtype  HWaddress           Flags Mask            Iface
    192.168.1.1              ether   00:18:01:6c:03:5f   C                     eth0
    [myuser@mydesktop ~]$

    This looks more like it. After all this my question is: What could I have done to flush a cache or reset the network to allow a simple reconnection w/o incident? I'm running Ubuntu 9.10, I removed network manager.


    [myusertmydesktop ~]$ uname -a
    Linux mydesktop 2.6.31-20-generic #58-Ubuntu SMP Fri Mar 12 04:38:19 UTC 2010 x86_64 GNU/Linux
    [myuser@mydesktop ~]$

    [myuser@myudesktop ~]$ cat /etc/network/interfaces
    auto lo
    iface lo inet loopback
    auto eth0
    iface eth0 inet static
    address 192.168.1.120
    broadcast 192.168.1.255
    network 192.168.1.0
    netmask 255.255.255.0
    gateway 192.168.1.1
    mtu 1492
    [myuser@mydesktop ~]$



    Thanks,
    Skaramanger
    M2N-SLI with AMD Phenom II X4 940 8GB of 400Mhz 128bit DDR2 RAM, an Evga GTX560ti Video card Phoenix Bios Rev. 5001

    Kubuntu 12.10 (do-release-upgrade)

  2. #2
    Join Date
    Dec 2007
    Location
    The last place I look
    Beans
    Hidden!
    Distro
    Ubuntu 10.04 Lucid Lynx

    Re: Strange network connection.

    lots of apps use local only network ports to allow processes to communicate with eachother. what ports are these connections to, and if you run netstat, what apps are they connected to?

    theoretically an arp flood could do weird things to your arp table, but somone would have to be able to get onto your local network to initiate one.
    Last edited by doas777; March 26th, 2010 at 09:41 PM.
    Things are rarely just crazy enough to work, but they're frequently just crazy enough to fail hilariously.

  3. #3
    Join Date
    Jun 2006
    Location
    USA
    Beans
    151
    Distro
    Kubuntu 12.04 Precise Pangolin

    Re: Strange network connection.

    doas777 thanks for your reply,

    Quote Originally Posted by doas777 View Post
    lots of apps use local only network ports to allow processes to communicate with eachother. what ports are these connections to, and if you run netstat, what apps are they connected to?

    Ooops, I failed to make clear that that theses connections were to my local ip from an outside source. They were definitely not from local host to itself. I did use zenmap to check a couple of those ips, but I didn't save them and rebooting did clear up the problem.


    theoretically an arp flood could do weird things to your arp table, but somone would have to be able to get onto your local network to initiate one.
    Yeah, is there a way to clear the arp cache? I have 2 firewalls running one on my router and shorewall on my box. My router's wireless is security is set to use wpa.

    Thanks again
    M2N-SLI with AMD Phenom II X4 940 8GB of 400Mhz 128bit DDR2 RAM, an Evga GTX560ti Video card Phoenix Bios Rev. 5001

    Kubuntu 12.10 (do-release-upgrade)

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