SUMMARY: Problem with ifconfig -alias

From: Thomas Leitner (tom_at_radar.tugraz.at)
Date: 12/15/04

  • Next message: Randy Rodgers: "SUMMARY: Problems with Tru64 UNIX V5.1B installation GUI on AS 2100" 
    Date: Wed, 15 Dec 2004 09:06:56 +0100
To: Tru64 Unix Managers <tru64-unix-managers@ornl.gov>

    Hi,

    Well, I did not find a solution, only a workaround (see below). Some
    people suggested to use a static host route on AMANDEV like this:

    # route add -host difsvrw1 gateway

    where gateway would be the aliased IP address. However this still does
    not work and TCP packets arrive with the main IP address at the
    destination rather than with the aliased IP address.

    Now my workaround was this: At the destination, add a static host route
    back to the MAIN IP address of AMANDEV. So my final working setup is this:

    - on AMANDEV:
       MAIN IP = 10.192.1.3
       ALIASED IP = 10.141.29.5

    - on DIFSVRW1
       MAIN IP = 10.141.29.3
       # route add -host 10.192.1.3 10.141.29.5

    So when TCP packets arrive at DIFSVRW1 with the (wrong) source IP
    10.192.1.3, DIFSVRW1 routes the answers back to 10.141.29.5 which is the
    correct IP.

    So in a nutshell: The bug in Tru64 persists but this workaround can be
    used in similar setups.

    Thanks to the following people for their replies:

    Michael James Bradford <mjbr@tdc.dk>
    Derek Haining <Derek.Haining@iLan.com>
    Thomas Cunningham <Thomas.Cunningham-02@scott.af.mil>
    Peter Gergen <petergergen@kpmg.com.au>

    Tom

    Thomas Leitner schrieb:
    >
    > Hi,
    >
    > I need to connect a development machine (DS20E, running Tru64 4.0G)
    > called AMANDEV to a test machine called DIFSVRW1 which has its IP
    > address in a different network. So I've used "ifconfig -alias" to give
    > AMANDEV an IP in the same network as DIFSVRW1.
    >
    > The problem is:
    >
    > 1.) I can ping AMANDEV from DIFSVRW1 and vice versa: This is OK
    > 2.) I can telnet from DIFSVRW1 to AMANDEV: This is OK
    > 3.) HOWEVER: I cannot telnet from AMANDEV to DIVSVRW1. This is *NOT OK*
    > and this is exactly what we need.
    >
    > Using an Ethernet sniffer we found out that for case 3) above,
    > the AMANDEV machine does not use the ALIASED IP address as the
    > source address. It rather uses the main IP address assiged to the
    > interface. This is the reason why DIFSVRW1 cannot answer to the
    > telnet packets.
    >
    > So this seems to be a bug in Tru64 4.0G (we're using the latest
    > patch kit already) that outbound TCP/IP calls to a network
    > over an aliased IP address does not get the proper source IP
    > address assigned.
    >
    > Any ideas anyone how to solve that?
    >
    > Thanks // Tom
    >
    >
    >
    >
    >
    >
    >
    >
    >

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