VIPADYNAMIC - VIPAROUTE statement

A VIPAROUTE statement is used to select a route from a distributing stack or a backup distributing stack to a target stack. This route is used for distribution of all DVIPAs for which a matching dynamic XCF address, or ALL, was specified on a VIPADISTRIBUTE statement. This route is also used for forwarding packets to existing connections on a stack that contains the DVIPA in MOVING status. When processing a connection from the client, the sysplex distributor determines whether or not a matching VIPAROUTE statement has been specified. If it has, the best available route is determined using the normal IP routing tables. If no matching VIPAROUTE statement exists for that target, IP packets distributed by sysplex distributor to that target use dynamic XCF interfaces. Dynamic XCF interfaces include HiperSockets™ (iQDIO), IUTSAMEH for the same LPAR, or XCF interfaces created by the IPCONFIG DYNAMICXCF or IPCONFIG6 DYNAMICXCF statement. If the Cisco Multi-Node Load Balancing (MNLB) function is being used, the target IP address on a VIPAROUTE statement is used to route the packet directly to the target stack if a matching VIPAROUTE statement has been specified.

Rule:

Ensure that the MTU value on the routes that are to be used is at least 604 (specify 1308 for IPv6). Lower MTU values can impact network performance and might result in loss of connections.

Result: There is always a matching route (and thus no message) if you define a default route by specifying DEFAULT.

If the VIPAROUTE statement specifies a target IP address for which no route exists, an informational message is issued the first time the problem is encountered. When this happens, that target is not considered for the distribution, and the distributor treats this the same way as when the dynamic XCF interface becomes inactive. If OMPROUTE is used for dynamic routing on the target, the GLOBALCONFIG SYSPLEXMONITOR DELAYJOIN TCP/IP profile option should be considered. The DELAYJOIN option delays the processing of sysplex-related definitions within the TCP/IP profile statements until OMPROUTE is active.

In the following cases, even though a VIPAROUTE statement has been specified, the dynamic XCF interface is used for distribution:

A target IP address that is not owned by the target stack is specified
The defined dynamic XCF address is for a pre-V1R7 target stack

Messages are issued at the distributing stack when these conditions are detected, and when the distributing stack first attempts to route a connection request to the target stack.

An additional case where the dynamic XCF interface is used even though the VIPAROUTE parameter has been specified is for a connection that is protected by an IPSec UDP-encapsulated security association negotiated with a peer behind a NAT.

Syntax

Rule: Specify the parameters in the order shown here.


              .-DEFINE-.                            
>>-VIPAROUTE--+--------+--dynxcfip--target_ipaddr--------------><
              '-DELEte-'

Parameters

DEFINE

Specifies that sysplex distributor should use the target IP address (target_ipaddr) to find the best available route to reach the target stack defined by the dynxcfip parameter. The target IP address can be any address in the HOME list of the target stack except for a dynamic VIPA (DVIPA) or a loopback address.

DELETE

Specifies that a previously defined VIPAROUTE statement should be deleted. sysplex distributor processing for the target stack specified by the dynxcfip parameter reverts to using dynamic XCF interfaces for existing and new connections after approximately 60 seconds.

dynxcfip

Specifies the IPv4 or IPv6 dynamic XCF address that uniquely identifies a target stack. The address is defined with an IPCONFIG DYNAMICXCF or IPCONFIG6 DYNAMICXCF statement on that target stack.

If duplicate dynxcfip values are specified (with different target_ipaddr values) with the DEFINE function in the same profile, the first entry is in effect. Any duplicate entries are ignored and a message is displayed.

See Restrictions on IPv6 addresses configured in the TCP/IP profile for a list of restrictions that must be observed when specifying this parameter for IPv6 dynamic XCF addresses.

target_ipaddr

Specifies any fully qualified IPv4 address (in dotted-decimal format) or fully qualified IPv6 address (in colon-hexadecimal format) in the HOME list of the target stack except for a dynamic VIPA (DVIPA) or a loopback address. The value is a static VIPA, a dynamic XCF address, or a real IPv4 or IPv6 address associated with a physical interface. See Restrictions on IPv6 addresses configured in the TCP/IP profile for a list of restrictions that must be observed when specifying this parameter for IPv6 addresses. This IP address is used as a destination address for a target stack to obtain the best available route from the sysplex distributor to the target stack.

Specifying a static VIPA for this address might achieve the highest degree of fault tolerance. This alleviates the single point of failure issue with non-VIPAROUTE statement use of dynamic XCF interfaces. If an IP address is specified that is not owned by the target stack, dynamic XCF interfaces are used to distribute IP packets to this target stack.

For more information about the use of the routing information, see z/OS Communications Server: IP Configuration Guide.

Steps for modifying

To remove the current configured statement, specify the VIPAROUTE DELETE statement with the same dynxcfip value and the same target_ipaddr value in a configuration data set referenced by a VARY TCPIP,,OBEYFILE command.
To change the current configured statement, you must specify the VIPAROUTE DELETE statement with the same dynxcfip value and the same target_ipaddr value first, and then specify the VIPAROUTE DEFINE statement with the same dynxcfip value and the different target_ipaddr value referenced by a configuration data set on a VARY TCPIP,,OBEYFILE command.
If the VIPAROUTE statement is changed, it affects active as well as new connections. For example, if an active connection is being distributed across dynamic XCF interface, and a VIPAROUTE DEFINE statement is defined for that target which results in the distributor selecting a route to the target over a different interface, then the active and new connections begin to use that new interface after approximately 60 seconds. If the previously defined VIPAROUTE statement is deleted, then active and new connections begin to use dynamic XCF interfaces after approximately 60 seconds.

Examples

This example shows how to define an alternate route to dynamic XCF for the sysplex distributor function.

VIPAROUTE 201.3.10.10 199.3.10.1
VIPAROUTE 2001:ODB8::201:3:10:10   2001:ODB8::199:3:10:1