How to set my Linux machine to have two network cards with two IPs

Discussion in 'Linux Networking' started by keanewoon, May 27, 2007.

  1. keanewoon

    keanewoon Guest

    Dear all gurus out there,

    I am newbie to Linux and networking.

    I have a Red hat linux that used as a Database machine, oracle.

    I have 2 network cards that I wish to set to and respectively, the default gw is The
    connection of the two IPs coming from 2 different switches (still from
    the same router).

    My purpose is that : if one of the switches is down, my connection
    still up with the other side.

    I know switch is hardly "down", but i wish to have full redundancy.

    What I did is, I jus set the 2 network cards with the two IPs and I
    switch off one of the switches, "poof" the whole network, how can it be done ?

    Or any other alternatives ?

    keanewoon, May 27, 2007
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  2. On Sun, 27 May 2007 02:02:58 -0700, keanewoon wrote:

    [link failover]
    Try the 'bonding' driver:

    And use an interface alias if you still need the second IP adress, e.g.:
    ifconfig bond0:1 <ipadress> ...
    Menno Duursma, May 27, 2007
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  3. Google bonding network interfaces...

    You need to have one ip address that is on both switches and will move
    from a primary to a seconday NIC.

    Intel had it's own IANS software on the older Linux versions but is now
    supporting standard bonding. On the 2.4 the Intel stuff was nice but
    required at least one Intel NIC per bonded pair.

    William Pechter, May 27, 2007
  4. keanewoon

    Tim S Guest

    Follow on from this:

    Caveat: I have only done bonding with 802.3ad for the purposes of link
    aggregation (enhanced bandwith), not for failover.

    I agree that bonding is probably the neater solution (only ever have one IP)
    and I believe that a suitable way would be to use the arp monitoring
    failover mode in the linux bonding module. Wanring though: don't just set
    up a bonded link in aggregation mode willy nilly or there is going to be
    much network weirdness resulting (arp confusion for one). The "ultimate"
    documentation can be found in the linux source here:


    To the OP - when you have a solution, I would recommend that you test it
    thoroughly with 2 tcpdump sessions bound each to one NIC and see if it is
    really behaving as you expect. Link aggregation requires support from the
    switch infrastructure and I've never come across link aggregation working
    where the links feed two different switches. Failover should howvere work
    with any kit, though you might get a pregnant pause when the primary link
    fails and the switches have to re-discover the path, but that shouldn;t be
    more than a few seconds IME.


    Tim S, May 27, 2007
  5. keanewoon

    momo Guest

    this configuration is not a linux issue your configuration is fine
    but will not support your target to make a fail over
    to make the data base client to use both IP's configure the client
    tnsnames.ora to fail over the other IP if one faild
    the 2nd and the most important is the however your connection
    will be established again but you will loose your session
    to avoid such issue you should use a caching library in your code
    (application) such as oci or jdbc.
    one more thing if you really want to make complete redundant use RAC
    as the instance is more critical than the switch
    momo, May 28, 2007
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