A fix is available
APAR status
Closed as program error.
Error description
A ping to a specific IP address will time out. A TCP or UDP connection will work to the same IP address, such as a FTP or Telnet session. TCPIP is receiving the ICMP packet, but does not reply to the packet. A routing table entry is flagged as a destination cache which will be deleted soon, but there are actual routes assoicated with the entry. . VERIFICATION STEPS: 1) Only ICMP traffic fails to the host 2) A ctrace with option ROUTE option will show a route is returned, but the rtp_dcache_cleanup bit is on in the RTOP. . KEYWORDS: RTE RTOP route ping icmp timeout not responding
Local fix
Recycle Omproute to rebuild the routing table
Problem summary
**************************************************************** * USERS AFFECTED: All users of the IBM Communications Server * * for z/OS Version 1 Release(s) 10, 11, and 12 * * IP: PATHMTUDISCOVERY * **************************************************************** * PROBLEM DESCRIPTION: Outbound ICMP response is not sent but * * TCP and UDP connections to the same * * remote address work. In order to hit * * this problem PATHMTUDISCOVERY must be * * enabled on the IPCONFIG profile * * statement. * **************************************************************** * RECOMMENDATION: * **************************************************************** Outbound ICMP response is not sent but TCP and UDP connections to the same remote address work. In order to hit this problem PATHMTUDISCOVERY must be enabled on the IPCONFIG profile statement. PATHMTUDISCOVERY causes the TCP/IP stack to generate destination cache entries for every TCP connection remote IP address to hold the minimum MTU. The garbage collection timer periodically deletes destination cache entries that are no longer in use. The delete process creates a chain of routing nodes to be deleted and then removes them one at a time. During the removal process the routing nodes and associated information may shift. If a node in the destination cache delete chain is shifted it may result in the node not being removed from the routing tree. When this occurs the rtp_dcache_cleanup flag will remain on and if a matching host route is added to the remote destination this flag will prevent the route from being usable by EZBIPFRH. The ICMP outbound response flow uses EZBIPFRH to locate a route to the destination and may result in discarded outbound ICMP response packets due to no selectable route being found. +-------------------------------------------------------------+ + 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
EZBIPRTE and EZB6PRTE have been amended to remove destination cache entries one at a time from the routing tree. The traversal of the routing tree is re-driven each time a node is deleted to ensure any shift resulting from the delete does not effect the next node selection or removal process. * Cross Reference between External and Internal Names
Temporary fix
Comments
×**** PE12/02/06 FIX IN ERROR. SEE APAR PM57513 FOR DESCRIPTION
APAR Information
APAR number
PM33467
Reported component name
TCP/IP V3 MVS
Reported component ID
5655HAL00
Reported release
1A0
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2011-02-23
Closed date
2011-03-25
Last modified date
2012-03-05
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
UK66154 UK66155 UK66156 PM37586
Modules/Macros
EZBIPRTE EZBPTREE EZB6PRTE
Fix information
Fixed component name
TCP/IP V3 MVS
Fixed component ID
5655HAL00
Applicable component levels
R1A0 PSY UK66154
UP11/05/11 P F105
R1B0 PSY UK66155
UP11/05/11 P F105
R1C0 PSY UK66156
UP11/05/11 P F105
Fix is available
Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.
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Document Information
Modified date:
05 March 2012