Preventing Listener's hand-off

Question

Scenario:
Oracle 10.2.0.4 RAC server.
Certain clients (running Oracle 10.1.0.4 SE) connect via a self rolled NAT load balancing firewall (long story - bottom line is that there is no real better way given the complex networking infrastructure these specific clients run in).
If the client is for example from subnet a.b.c, it will be "redirected" (IP packet header rewritten using NAT) to a specific RAC node.
Problem description:
This is working fine (for some years now) - but the specific Oracle client (on subnet a.b.c) needs to know which RAC node it is being redirected to. It needs to specify the SID of that RAC instance in the TNS connection string. Why? Using the SID forces the listener on that node to accept the client's connection without handing it off to another listener and another instance on another node.
And this is a problem ito high availability. That specific node may not always be available (and we can auto configure the NAT firewall to send traffic from subnet a.b.c to a different node all together).
Ideally we want to use the SERVICE_NAME instead, but without any form of Oracle listener load balancing, fail over or being handed off to another instance.
If the client connects to a listener using SERVICE_NAME "foo", we want the Listener to accept that (as "foo" is a registered service by the local instance). We do not want the listener to arbitrarily select another RAC node instance (also servicing "foo") and redirect the client's connection there.
However, does not matter how the TNS is configured with SERVICE_NAME (and explicitly disabling load balancing and so on). the listener mostly will hand off the connection to another listener - and the client will then throw a "+ORA-12545: Connect failed because target host or object does not exist+" as it is unable to reach the IP supplied by the listener.
Trust that I explained this well enough... bottom line is that we want to tell the listener, via a SERVICE_NAME connection string, not to hand the connection over to another listener. Simple as that. But despite trying a number of config setting and hunting through the Oracle Network ref guide, it does not seem to be simple at all...
Any ideas, comments and suggestions will be appreciated. Thanks.

Answer 1

Toni Lazarin wrote:
Did you try setting the DIRECT_HANDOFF_TTC_<listenername>=OFF in the listener.ora ?Thanks. Tried it, did not make any difference.
It is also not listed as a parameter in Oracle® Database Net Services Reference guide. Which made me wonder if is is still supported with 10.2.
I had a look on Metalink (using direct hand-off as search criteria) and run into utterly useless note 90707.1 - Connecting to Database Through a Network Address Translator (NAT). Which describes the exact issue I have, but does not provide any tangible solutions or references on how to solve it in my case. There is a reference to another note (dealing with firewalls) which mentions in passing "+In dedicated server mode, Unix natively implements TCP/IP sharing, so there should be no problem with connectivity+". Now if we assume that direct handoff is by default on for Unix/Linux, then the problem I have is with the Listener load balancing and causing a redirect when the client wants no load balancing at all. Thus it would seem to be a RAC listener specific problem.
Using CMAN is not an option. Do not want to introduce even more s/w layers for the connectivity tier - besides, the NAT firewall works just fine and does exactly what we want it to do. Now if only the RAC listeners will play ball and not send redirect hand offs to the client when using a service name to connect.
Any ideas on how to tell a listener not to load balance an incoming client connection and simply service and connect/hand-off that connection as the client states?