Global TCP/IP SOURCEIP

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Global TCP/IP SOURCEIP for Stand Alone Servers

The IBM Connect:Direct Server binds a local socket for out-bound processes and the default is to bind to the HOST IP as returned by BPX1HST (gethostid/gethostname) function. The HOST name is used for SMF reporting in the SESSION.HIGHWATER.SMF record. The HOST IP will become the local IP for the node.

To allow more control over the HOST IP assignment, the TCP.SOURCEIP initialization parameter can be used to specify the IP for default or global source IP. The intent of TCP.SOURCEIP is to define a global default IP address that the Connect:Direct for z/OS server can bind to for out-bound IP processes so that each individual NETMAP entry does not require the SOURCEIP parameter unless there is a requirement to override the default. An outbound process will bind to an IP obtained from the following places:
  • NETMAP SOURCEIP parameter
  • TCP.SOURCEIP INITPARM
  • Hostname
TCP.SOURCEIP does not support ANYADDR or 0.0.0.0 as source IP, so to provide compatibility with previous releases, which assigned the local or host IP differently, TCP.SOURCEIP=1STLISTEN is available to modify the default. 1STLISTEN will cause Connect:Direct for z/OS to use the first IP in the TCP.LISTEN parameter list instead of the IP returned by BPX1HST. If the first IP in TCP.LISTEN is ANYADDR or 0.0.0.0, the bind function will select the first IP in the TCP stack, usually the stack home address.
Note: Services do not currently exist to obtain a hostname for IPv6.

Global TCP/IP SOURCEIP for CD/PLEX Servers

Since CD/PLEX servers can run on multiple LPARs, each with its own TCP/IP stack, a different approach must be used for a global source IP. Normal defaults will assign a different HOST IP for the manager and each server based on the local TCP/IP stack. The TCP.SOURCEIP initialization parameter override this TCP/IP restriction.

However, IBM TCP/IP provides a feature called Distributed DVIPA that allows a single Dynamic VIPA address to be shared across TCP stacks and LPARs in a Sysplex. Please refer to “z/OS Communication Server: IP Configuration Guide” for information about Distributed DVIPA. With Distributed DVIPA configured for all TCP/IP stacks in a Sysplex and the Distributed DVIPA address included in TCP.LISTEN, TCP.API.LISTEN and TCP.SOURCEIP, the CD/PLEX manager and servers can use the same IP for primary and backups (Extended Recovery) and can be moved to any LPAR in the Sysplex as needed.