IBM Support

PH36755: BACKUP LB MAY RECEIVE CLUSTER TRAFFIC

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APAR status

  • Closed as program error.

Error description

  • If there are multiple takeovers, arp tables may not update
    correctly to route packets to the active load balancer.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:  IBM WebSphere Application Server Edge Load  *
    *                  Balanacer for IPv4 and IPv6 users           *
    ****************************************************************
    * PROBLEM DESCRIPTION: With Load Balancer high availability    *
    *                      configured, the active load balancer    *
    *                      may not receive traffic.                *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    With high availability configured between load balancers,
    traffic may be directed to the standby load balanacer by
    routers instead of the active load balancer. The standby load
    balancer discards the traffic. Traffic is not forwarded.
    

Problem conclusion

  • When a load balancer issues a takeover to become the active
    load balancer, the load balancer broadcasts an ARP update
    which notifies routers to send cluster traffic to the new load
    balancer. If takeovers occur quickly between the load
    balancers such that multiple ARP updates are broadcast, the
    router may receive the updates in a different order such that
    it forwards traffic to the standby load balancer.
    
    Code change was made such that the standby load balancer
    notifies the active load balancer when transitioning into a
    standby state. When the active load balancer receives this
    notification, it broadcasts an ARP update for the cluster
    addresses again to ensure the router has the correct entry.
    
    Fix levels:
       8.5.5.20
       9.0.5.9
    

Temporary fix

Comments

APAR Information

  • APAR number

    PH36755

  • Reported component name

    WS EDGE LB IPV4

  • Reported component ID

    5724H8812

  • Reported release

    850

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2021-04-28

  • Closed date

    2021-05-03

  • Last modified date

    2021-05-03

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

Fix information

  • Fixed component name

    WS EDGE LB IPV4

  • Fixed component ID

    5724H8812

Applicable component levels

[{"Line of Business":{"code":"LOB10","label":"Data and AI"},"Business Unit":{"code":"BU029","label":"Software"},"Product":{"code":"SSEQTP","label":"WebSphere Application Server"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"8.5"}]

Document Information

Modified date:
04 May 2021