Example

This example uses the SOURCEVIPA option for outbound datagrams originating at a z/VM® TCP/IP stack.

Select a virtual IP address in the HOME statement as the local address. The address that most closely precedes a physical IP address is used as its local address.

Example:

     HOME
       172.2.1.1     VIPA1  ; <-- Source for LINK2 and LINK1
       151.2.3.1     LINK2
       151.4.1.1     LINK1
       172.2.1.2     VIPA2  ; <-- Source for LINK7 and LINK6
       151.2.3.2     LINK7
       151.4.1.2     LINK6

Optionally, additional virtual IP addresses can be defined to associate a group of interfaces and serve as local addresses. VIPA1 and VIPA2 are examples of virtual links; the remaining entries are examples of actual links that are associated with physical IP addresses. Virtual IP addresses are used in outbound IP datagrams. For more information see ASSORTEDPARMS Statement. If you specify SOURCEVIPA on the ASSORTDPARMS statement, link VIPA1 provides the virtual IP address for LINK2 and LINK1, while link VIPA2 provides it for LINK7 and LINK6.

If an outbound datagram is not to contain a source virtual IP address for a particular interface (that is, a physical IP address should always be used), the address and link entries must be suitably ordered, as shown in the following example.

     HOME
       151.4.1.1     LINK1  ; <-- No SOURCEVIPA for outbound on LINK1
       172.2.1.1     VIPA   ; <-- Source for ETH1 and LINK6
       151.2.3.1     ETH1
       151.4.1.2     LINK6

Table 1 shows how various TCP/IP protocols use a virtual IP address when it is specified as a local address. "Y" indicates that the address will be used as the local address, and "N" indicates that it will not be used as the local address.

Table 1. Source VIPA Usage Chart
Destination	ICMP	TCP	RAW	UDP
Local Interface	N	N	N	N
Local network	Y	Y	Y	Y*
Remote network	Y	Y	Y	Y
Note: * Except for RIP packets