Question & Answer
Question
We would like our z/OS host to act like a router. What is needed to enable IP forwarding on z/OS host?
Answer
On a z/OS TCPIP stack enabled for IPv4, IP Forwarding is enabled by specifying IPCONFIG DATAGRAMFWD parameter in the TCPIP profile, or letting IPCONFIG default to DATAGRAMFWD.
On a z/OS TCPIP stack enabled for IPv6, IP Forwarding is enabled by specifying IPCONFIG6 DATAGRAMFWD or letting IPCONFIG6 default to DATAGRAMFWD.
DATAGRAMFWD permits the forwarding of IP packets that are received by, but not addressed to, the stack.
It should be noted that, to allow the distributing IP stack to distribute dynamic VIPAs, it is not required to enable IP forwarding using the IPCONFIG (or IPCONFIG6) DATAGRAMFWD TCP/IP profile statement.
IPv4 IP Forwarding
When IP forwarding is in effect, there are multiple equal-cost routes to the destination, and the NOFWDMULTIPATH parameter of IPCONFIG is specified or defaulted, TCP/IP uses the first active route found for forwarding each IP packet. The DATAGRAMFWD NOFWDMULTIPATH parameter is confirmed by the message:
EZZ0641I IP FORWARDING NOFWDMULTIPATH SUPPORT IS ENABLED
When forwarding is in effect, there are multiple equal-cost routes to the destination, and the FWDMULTIPATH PERPACKET parameter is specified, TCP/IP selects a route for forwarding each packet on an approximate round-robin basis from the multiple equal-cost routes. The DATAGRAMFWD FWDMULTIPATH PERPACKET parameter is confirmed by the message:
EZZ0641I IP FORWARDING FWDMULTIPATH PERPACKET SUPPORT IS ENABLED
IPv6 IP Forwarding
When forwarding is in effect, there are multiple equal-cost routes to the destination, and the NOFWDMULTIPATH parameter is specified or defaulted, TCP/IP uses the first active route found for forwarding each IP packet. The DATAGRAMFWD NOFWDMULTIPATH parameter is confirmed by the message:
EZZ0700I IPV6 FORWARDING NOFWDMULTIPATH SUPPORT IS ENABLED
When forwarding is in effect, there are multiple equal-cost routes to the destination, and the FWDMULTIPATH PERPACKET parameter is specified, TCP/IP selects a route for forwarding each IP packet on an approximate round-robin basis from the multiple equal-cost routes. The DATAGRAMFWD FWDMULTIPATH PERPACKET parameter is confirmed by the message:
EZZ0700I IPV6 FORWARDING FWDMULTIPATH PERPACKET SUPPORT IS ENABLED
OSA Port-sharing
When an OSA-Express feature is being shared between multiple stacks (OSA port sharing), OSA allows two TCP/IP stacks sharing the port to act as IP routers: a PRIMARY stack and a SECONDARY stack.
To enable a TCP/IP stack to act as a router, configure one of the OAT entries as PRIMARY, and enable IP forwarding e) on the TCP/IP stack acting as PRIMARY. Likewise, to enable a second stack to back up the PRIMARY router, configure one of the OAT entries as SECONDARY, and enable IP forwarding on the stack acting as SECONDARY.
Product Synonym
ZOSCS COMMSERVER
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Document Information
Modified date:
03 August 2016
UID
dwa1292579