[load balancing] BigIP: Recommended solution to load balance Nodes on different subnets?

From: Pranav Kantawala (p_kantawalaIZZATyahoo.com)
Date: Thu Jan 30 2003 - 14:09:03 EST

  • Next message: Gregory, Brad: "RE: [load balancing] BigIP: Recommended solution to load balance Nodes on different subnets?"

    Hi,

    I'm trying to find out the recommended solution to
    load balance Nodes on any subnet, without BIGIP
    having an IP interface on that subnet. I'm using
    'BIG-IP Kernel 4.2'.

    For instance, I have the BIGIP on subnet S1, and Nodes
    A and B on subnet S2 and S3 respectively.
    Traffic from Nodes A and B to other nodes in the
    network may bypass the BIGIP. I would like to
    define a Virtual Server VS1 to load balance a service
    on Nodes A and B.

    I was able to achieve this using SNAT configuration as
    follows:
    1. I defined only one VLAN (external) on the BigIP.
    2. I defined a default SNAT with a publicly accessible
    IP address as the translation address.
    3. I defined a pool, lb_pool with two nodes A and B.
    4. I defined a Virtual Server VS1 that uses pool
    lb_pool.

    The client is on a completely different subnet. When
    client makes a connection to VS1, the BIGIP
    translates the Source IP to SNAT address, and
    Destination IP to Node Address (either A or B).
    Thus, the Nodes always see the source as the SNAT
    address.

    I had to define SNAT, because without it, the Virtual
    Server definition instructs the BIGIP to
    translate only the Destination IP address, and not the
    Source IP address in packets. In doing so,
    the return traffic from nodes back to the client could
    bypass the BIGIP resulting in the client
    dropping the connection.

    Are there any limitations imposed by the Source IP
    translation with SNAT? Is persistence
    configuration affected by this (for example, Client IP
    based persistence)? Are there any other
    restrictions when using SNAT to load balance Nodes on
    different subnets? If this is not the
    recommended solution, could you please suggest an
    alternative?

    Thanks,
    Pranav

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