PH02596: EDGE LOAD BALANCER FOR IPV4 AND IPV6 V9.X - POTENTIAL FOR LONG OUTAGE OF CLUTERIP AFTER AN HA FAILOVER.

9.0.0.10: WebSphere Application Server traditional V9.0 Fix Pack 10
8.5.5.15: WebSphere Application Server V8.5.5 Fix Pack 15
9.0.0.11: WebSphere Application Server traditional V9.0 Fix Pack 11
9.0.5.0: WebSphere Application Server traditional Version 9.0.5 Refresh Pack
9.0.5.1: WebSphere Application Server traditional Version 9.0.5 Fix Pack 1
9.0.5.2: WebSphere Application Server traditional Version 9.0.5 Fix Pack 2
8.5.5.17: WebSphere Application Server V8.5.5 Fix Pack 17
9.0.5.3: WebSphere Application Server traditional Version 9.0.5 Fix Pack 3
8.5.5.20: WebSphere Application Server V8.5.5.20
8.5.5.18: WebSphere Application Server V8.5.5 Fix Pack 18
8.5.5.19: WebSphere Application Server V8.5.5 Fix Pack 19
8.5.5.16: WebSphere Application Server V8.5.5 Fix Pack 16
8.5.5.21: WebSphere Application Server V8.5.5.21

APAR status

• Closed as program error.

Error description

• After a failover, packets may be directed to the previously
  active load balancer instead of the currently active load
  balancer. If this occurs, traffic will not be forwarded until
  the router's ARP entry for the cluster IPs expires.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:  IBM WebSphere Application Server Load       *
  *                  Balancer for IPv4 users                     *
  ****************************************************************
  * PROBLEM DESCRIPTION: With highavailability, the load         *
  *                      balancer issues a gratuitous arp        *
  *                      which may not be honored by the         *
  *                      routers.                                *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  Gratuitous arps are a special message with the arp protocol
  used to notify machines with a current entry for the IP
  address to use a new physical address.
  

Problem conclusion

• Arp messages are either request messages or reply messages. A
  gratuitous arp is really neither a request or a reply; it is
  not requesting anything information nor is it answering any
  request but an operating (request or reply) must be specified
  in the messaage.
  
  The load balancer was setting "reply" as the operation but
  some routers do not accept grat arps with the reply opcode by
  default so code as been modified to issue two grat arps for
  each cluster on a takeover, one with the opcode reply and the
  other with the opcode request to ensure routers update their
  arp cache to route packets to the newly activated load
  balancer.
  
  Fix levels:
      8.5.5.15
      9.0.0.10
  

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

• R850 PSY

     UP

• R900 PSY

     UP