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Thread: asymetric ping behaviour

  1. #1
    Join Date
    Dec 2019
    Beans
    2

    asymetric ping behaviour

    There are two hosts in my network, A and B. If I ping A from B, I get "Destination Host Unreachable".
    Ping from A to B succeeds.
    After the successful ping from A to B, ping from B to A succeeds too, but only as long as B does not loose the connection (by going to sleep) and reactivates the connection after resume.
    Host A is a Raspberry Pi running raspian, host B a PC running ubuntu 18.04
    This behaviour is new, since I installed alsamixer on the Pi, but I doubt that there is a connection.
    When the ping doesn't work, also A is not seen by Angry IP Scanner running on B, after the successful reverse ping it IS seen.
    Any ideas what causes this weird behaviour and how to fix it?

  2. #2
    Join Date
    Mar 2010
    Location
    Squidbilly-Land
    Beans
    Hidden!
    Distro
    Ubuntu Mate 16.04 Xenial Xerus

    Re: asymetric ping behaviour

    What is the network topology? If same subnet, then only ethernet and ARP tables are being used.
    Ping by IP or hostname?
    Is /etc/hosts setup on both systems so they know about each other?
    Any wifi involved?
    Is IPv6 enabled or not?

  3. #3
    Join Date
    Dec 2019
    Beans
    2

    Re: asymetric ping behaviour

    Quote Originally Posted by TheFu View Post
    What is the network topology? If same subnet, then only ethernet and ARP tables are being used.
    Ping by IP or hostname?
    Is /etc/hosts setup on both systems so they know about each other?
    Any wifi involved?
    Is IPv6 enabled or not?
    Both computers are in the same subnet: 192.168.2.*
    /etc/hosts entries are correct, ping by IP and by hostname makes no difference.
    Connections are via wlan.
    IPv6 enabled? How do I check?

    It seems, the behaviour described appeared after using rdesktop for connecting once. Rebooting fixed it - should I have tried earlier.

  4. #4
    Join Date
    Apr 2013
    Beans
    28

    Re: asymetric ping behaviour

    I now see that rdesktop was NOT the cause and rebooting fixes the problem only temporarily.
    After a while (maybe some days) host A can again not be accessed from host B, though both are connected to the network.
    Pinging B from A fixes the problem.
    Interestingly, the first ping-reply takes about 2 seconds, the following ones about 6 milliseconds.
    Any ideas?
    Last edited by ulrichmuc; 6 Days Ago at 11:38 AM.

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