PH11040: NAT CONNECTIONS FAIL UNDER HEAVY LOAD

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

• LB reports no ephemeral ports available but there are free
  ports so the connections should not fail.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:  IBM WebSphere Application Server Load       *
  *                  Balancer for IPv4 and IPv6 users            *
  ****************************************************************
  * PROBLEM DESCRIPTION: NAT forwarding may fail under heavy     *
  *                      stress                                  *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  NAT fowwarding requires the load balancer to open a new
  connection between the return address and the server IP. The
  load balancer keeps a pool of available ports (ephemeral
  ports) to use for these connections. The pool is not
  thoroughly searched for an available port so a connection may
  fail reporting that no ports are available when there are free
  ports. When this occurs, messages will be reported in
  different locations depending on the operating system used:
  for linux, /var/log/messages will indicate the connection
  failure; on windows, the ibmlb2.log will indicate the
  conenction failure; on AIX, the message is stored in the
  executor trace memory and can be displayed by extracting the
  trace with the lbext command.  On all operating systems, the
  executor will show an increase in "Packets discarded" when
  this occurs.
  

Problem conclusion

• A fix was made to ensure that the available ephemeral port
  table is accurately searched for available ports. This
  problem
  and fix applies to the load balancer for ipv4 and ipv6 only
  (ULB).
  
  Fix levels:
      8.5.5.16
      9.0.5.0
  

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