Re: Intermittent Routing Problem

From: Jeff Liebermann (jeffl_at_comix.santa-cruz.ca.us)
Date: 04/05/04

  • Next message: David P. Lurie: "Re: sftp2 cleint" 
    Date: Sun, 04 Apr 2004 21:57:06 -0700

    On Mon, 05 Apr 2004 15:54:59 +1200, David Kirk
    <davidrkirk.NOSPAM@hotmail.com> wrote:

    >That is the whole point of this change. Our local LAN uses
    >192.100.100.0/24 which is owned by other people out there on the
    >Internet. We are moving to the 192.168.1.0/24 subnet.

    No problem. However, you're doing it all wrong. You really should
    look into a VPN. I struggled with shovelling multiple socket based
    services through a single IP address with routeing in the past and
    have literally given up. It can be done, but it's not worth the
    effort. A VPN is the only way to fly. You get all the benifits of an
    encrypted data stream (something you don't get with just routeing) as
    well as a totally transparent LAN, where all the IP socket numbers at
    both ends are visible.
    (End of sales pitch).

    >>Was this working properly *BEFORE* you twiddled with the IP addresses?
    >
    >Yes, but we only had a single subnet, so we didn't even have a gateway
    >setup.

    Ok, so this is essentially a new topology.

    >The printer is a network printer. It is not attached to the SCO box
    >directly. It has a JetDirect card in it. The end of day reports get
    >stuck in the print queue until something (I don't know what) allows
    >the server to connect to the remote printer.

    The default setup for JetDirect boxes is to have the IP address
    assigned by DHCP. Are you sure that the printer has the desired IP
    address? Are you sure that it will stay that way? I suggest you
    either use a "static DHCP" assignment, or a static IP address in the
    print server.

    >The problem is that hosts on the old subnet (including the printer)
    >cannot connect to the server and vice versa. Telnet, ping, printing,
    >etc don't work between subnets.

    Yep. That's the way it's suppose to work between sub-nets. The whole
    idea behind subnets is to seperate the traffic. If you plugged both
    subnets into the same network without the router, you still would not
    be able to communicate. The router(s) need to provide the connection
    between the two networks. Think VPN.

    >> Can you ping the remote printer?
    >No.

    Ok. Let's start at the printer and work backwards to see where things
    stop. I already know the answer but the method will be necessary for
    testing when you get it together.
    1. Can you ping the print server from a local PC on the local
    network?
    2. If yes, can you ping it from the SCO box?
    3. If yes, can you ping it from the remote router using Cisco's
    diagnostics?
    4. If yes, can you ping it from the internet? (not for VPN).
    5. If yes, can you ping it from the other router using Cisco's
    diagnostics?
    6. if yes, can you ping it from a workstation or server on the other
    network?

    Can you see how this works? Start at one end and work backwards
    toward yourself. Where the pings fail, is the problem.

    >I have another one that I am changing tomorrow morning. Hosts on the
    >new subnet can't ping or telnet to it.

    Same issue, same problem. That means that there's probably nothing
    defective in the hardware.

    >Did I mention that the problem is intermittent. This morning when I
    >came in to the office, I couldn't ping the server on the other subnet.
    >Sometime during my troubleshooting, it started working and has done
    >all day. The problem seems to only occur when no hosts on the other
    >network have communicated for some undetermined amount of time.

    Is this a dialup connection? The intermittants might be due to the
    line going down. You might wanna deploy some kind of network uptime
    or graphing program to check if the line is going up or down. I use
    MRTG and "Whats up". Dropping the connection when the traffic is low
    sounds like a router/dialup issue.

    You might also be suffering from excessive traffic. If one of your
    workstations has been compromised by a worm or other traffic
    generating junkware, it could simulate a dropped connection because it
    occupies all the bandwidth.

    >I've already found that the old broadcast address was still in
    >/etc/default/tcp.

    Keep going. There's more. Running
      netconfig
    and
      uname -S new_name
    changes most of the settings, but not all of them.

    >Both NIC and switch are forced to 100-FD.

    There's no guarantee that the SCO box will comply. What type of NIC
    is in the SCO boxes? I suggest you force the switch ports to 10barf-T
    half-duplex, or the lowest possible NWAY technology until you have
    everything working. You may need to power off the SCO box to get the
    NIC to reset.

    Good luck. 

    -- 
Jeff Liebermann  150 Felker St #D  Santa Cruz CA 95060
(831)421-6491 pgr  (831)336-2558 home
http://www.LearnByDestroying.com   AE6KS
jeffl@comix.santa-cruz.ca.us   jeffl@cruzio.com
  • Next message: David P. Lurie: "Re: sftp2 cleint"

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