Ephemeral ports

When running with multiple transport providers, just as it is necessary to synchronize PORT reservations for specific applications across all stacks, it is required to synchronize reservations for port numbers that will be dynamically assigned across all stacks. These are the ephemeral ports above 1023, which are assigned by the stack when none is specified on the application bind(). To reserve a group of ports in the PROFILE.TCPIP, use PORTRANGE. For more information about PORTRANGE, see TCP/IP Customization. Specify the same PORTRANGE for every stack. In addition, you must let the z/OS® UNIX CINET know which ports are guaranteed to be available on every stack. The following example reserves ports 40000 - 41999 in the two required files:

• PROFILE.TCPIP
  • PORTRANGE 40000 2000 TCP OMVS ; Reserved for OMVS
  • PORTRANGE 40000 2000 UDP OMVS ; Reserved for OMVS
• BPXPRMxx parmlib member
  • NETWORK DOMAINNAME(AF_INET)
  • INADDRANYPORT(40000)
  • INADDRANYCOUNT(2000)
  Notes:

  1. When IPv6 is configured and there are two NETWORK statements, INADDRANYPORT and INADDRANYCOUNT need to be specified only for the NETWORK statement for AF_INET and not for AF_INET6. If they are specified for AF_INET6, they are ignored and the values from the NETWORK statement for AF_INET are used if provided. Otherwise, the default values are used.
  2. In a CINET environment, you can use IBM® Health Checker for z/OS to check whether the range of ports specified by the INADDRANYPORT and INADDRANYCOUNT operands of the BPXPRMxx parmlib member is reserved for OMVS on the TCP/IP stack. For more information about IBM Health Checker for z/OS, see z/OS Communications Server: IP Diagnosis Guide.