Re: ARP Table wierdness

From: Pete Nesbitt (pete_at_linux1.ca)
Date: 11/14/03

  • Next message: Mark Bradbury: "Re: Listing lsat access times" 
    To: redhat-list@redhat.com
Date: Thu, 13 Nov 2003 17:33:13 -0800

    On November 13, 2003 03:36 am, Enrico Payne wrote:
    > Hi,
    >
    > I am running RH8 (Std ISO install) on 3 servers (kernel 2.4.18-14), and
    > have noticed a strange thing over the last few days.
    >
    > Sometimes the client pc's (Windoze) or the servers for that matter may not
    > be able to ping the one server. However if I do a traceroute, it knows
    > about it, as I get !H messages on the traceroute.
    >
    > If I check the arp table (arp -a), I can see the server I am trying to
    > ping, but it has an incomplete address.
    > If I manually add the server to the arp table (arp -s), then all is well.
    > What is strange is the fact that all the machines are on the same subnet
    > and other machines can ping the server no problem. Any amount of rebooting
    > does not seem to resolve the problem. This seems to be happening at random.
    >
    > I have also noticed an error on the server consoles "Neighbour table
    > overflow". Does this perhaps have something to do with it?
    >
    > Does anyone know what could be causing the ARP weirdness, and what is
    > causing the Neighbour table overflow error?
    >
    > Regards
    > Enrico Payne

    not sure on why this is intermittent, but !H is Host Unreachable. So is it
    just geting resolution from a local host file and failing to access the
    network?

    -can you clearify the situation a bit (you say "it knows about it" hmmm)
    -what exactly is in the incomplete entry of arp table?

    One thought, that may be unrelated, is that despite the way a switch should
    work (send out all other ports if unknown), I have seen situation where you
    had to "ping out" from a new machine to get it in the switches mac table,
    this is often the case when you move a box from one port to another, as the
    switches mac tables are wrong until it flushes the old info. Do you have
    anything like that that may be causing problems? 

    -- 
Pete Nesbitt, rhce
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