PK36156: EE LINK PATH SWITCH DUE TO SHORT REQUEST RETRY LIMIT EXHAUSTED AFTER IPL OR RESTART OF OMPROUTE.

Obtain the fix for this APAR.

APAR status

• Closed as unreproducible in next release.

Error description

• Path switch with message IST1494I occurs with reason
  IST1818I PATH SWITCH REASON: SHORT REQUEST RETRY LIMIT EXHAUSTED
  after EE link are activated before the TCPIP routing table is
  completely built.
  .
  1) The EE links are started during Vtam startup.
  2) Omproute has not learned all the routes when the EE link was
  started.  This caused a less specific route(subnet or default)
  route to be used for the EE link.
  3) A path switch occurred due to the packets being sent to next
  hop IP addresses which would not forward the packets to the
  destination.
  4) When a host route became available, the EE link did not
  switch to this route.
  .
  VERIFICATION STEPS:
  1) Use the ODPK of the failing CNR pipe to find the next hop
  IP address.
  2) Using Netstat Route, find the most specific route to the
  destination.
  3) Compare the next hop address from the ODPK to the next hop
  field from the Netstat Route.
  

Local fix

• Recycle the EE link by inactivating/activating the XCA major
  node.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of the IBM Communication Server    *
  *                 for z/OS Version 1 Release 7 & 8 IP:         *
  *                 Enterprise Extender                          *
  ****************************************************************
  * PROBLEM DESCRIPTION: If the Enterprise Extender (EE) link    *
  *                      is started before dynamic routing has   *
  *                      completely populated the routing table, *
  *                      then EE packets may be forwarded to an  *
  *                      incorrect next hop. As a result,        *
  *                      IST1818I is issued and the EE link is   *
  *                      unusable.                               *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  In the problem reported, EE links are started before the dynamic
  routing deamon has finished populating the routing table, and
  static or replaceable static routes are not present in the
  routing table. As a result, traffic for the EE interface will
  use a less specific route, such as a subnet or network route.
  This subnet or network route may or may not lead to the correct
  next hop for the EE traffic. If the route leads to the incorrect
  next hop, then an EE link path switch occurs, and eventually the
  request limit is exhausted resulting in no traffic reaching the
  other end of the EE link.
  
  The problem can be circumvented by having a replaceable static
  host route for the EE link in the routing table, or by recycling
  the EE link once the dynamic routing deamon learns a host route
  to the other end of the EE link.
  +-------------------------------------------------------------+
  + Please check our Communications Server for OS/390 homepages +
  + for common networking tips and fixes.  The URL for these    +
  + homepages can be found in Informational APAR II11334.       +
  +-------------------------------------------------------------+
  

Problem conclusion

Temporary fix

Comments

• Modules in the UDP and IP routing layers have been amended to
  detect routing table changes and select a more specific route
  when appropriate.
  

APAR Information

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

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

  UK22535 UK22536

Modules/Macros

• EZBIFIUM EZBIPRHD EZBUDBYP EZBZUDAT EZB6PRHD
  

Fix information

• Fixed component name

  TCP/IP V3 MVS

• Fixed component ID

  5655HAL00

Applicable component levels

• R170 PSY UK22535

     UP07/03/27 P F703

• R180 PSY UK22536

     UP07/03/27 P F703

Fix is available

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