PH36755: BACKUP LB MAY RECEIVE CLUSTER TRAFFIC

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 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