The OSA primary router support takes into consideration and interacts with the VLAN ID support (VLAN ID registration and tagging). OSA supports a primary and secondary router on a per VLAN basis (per registered VLAN ID). Therefore, if TCP/IP is configured with a specific VLAN ID and also configured as a primary or secondary router, that stack serves as a router for just that specific VLAN. This allows each OSA (CHPID) to have a primary router per VLAN. Configuring multiple primary routers (one per VLAN) has many advantages and preserves traffic isolation for each VLAN.
This support becomes more important when a single OSA is shared by multiple stacks. In this type of configuration, when each stack was configured with a unique VLAN ID, each stack could also be configured as a primary router for its respective VLANs.
OSA also continues to support a primary and secondary router that is not associated with a specific VLAN. This primary router is referred to as the default primary router. It continues to function as the router for inbound packets that are not VLAN ID tagged, or packets that are VLAN ID tagged with a VLAN ID that is not registered to OSA. This is the same primary router support that existed prior to introduction of the VLAN ID support. Therefore, multiple specific VLAN primary routers and a single default primary router can concurrently activate and share a single OSA.
Each VLAN-specific primary and secondary router is subject to the same OSA rules (that is, supporting a single primary router and allowing multiple secondary routers) as the default primary router.
Figure 1 shows a configuration where multiple TCP/IP stacks are sharing a single OSA, and multiple VLANs with primary routers are configured.
In this example, TCP/IP x serves as the default primary router (PRIRouter without a VLANID configured). The other three TCP/IP stacks serve as a PRIRouter for just their specific VLANs.
For additional information regarding the details and syntax for configuring a VLAN Identifier (VLANID), and how to configure a TCP/IP stack as a primary or secondary router, see z/OS Communications Server: IP Configuration Reference. For IPv4 information on the PRIRouter, SECRouter, NONRouter, and VLANID parameters, see DEVICE and LINK – MPCIPA OSA-Express QDIO devices or INTERFACE - IPAQENET OSA-Express QDIO interfaces. For IPv6 information regarding these parameters, see INTERFACE - IPAQENET6 OSA-Express QDIO interfaces.