ifLinkUp/ifLinkDown Traps and "override" Configuration

Hi,

I'm trying to understand the difference between using an "override" for setting the IF-MIB::ifLinkUpDownTrapEnable.<x> object vs. a traditional set. I find that when these columns are set for an ifXEntry via the override mechanism in the agent's configuration file I do not ever see the corresponding effect (wrt linkUp/linkDown traps being issued):

override -rw IF-MIB::ifLinkUpDownTrapEnable.4 integer 1

However, if I remove the override and instead set the MIB object via a traditional set the corresponding effect (linkUp/linkDown traps being issued) does indeed occur:

snmpset -v2c -c private -m ALL localhost IF-MIB::ifLinkUpDownTrapEnable.4 i 1

Indeed, when I step through the agent in the debugger I see the key conditional where this behaviour changes. This is in _check_interface_entry_for_updates() in ifTable_data_access.c:

...
    if (oper_changed) {
        rowreq_ctx->data.ifLastChange = netsnmp_get_agent_uptime();
#ifdef USING_IF_MIB_IFXTABLE_IFXTABLE_MODULE
        if (rowreq_ctx->data.ifLinkUpDownTrapEnable == 1) {
            if (rowreq_ctx->data.ifOperStatus == IFOPERSTATUS_UP) {
...

The 'data.ifLinkUpDownTrapEnable' data member is always 0 in the override case, however, it is always the correct value (1 in the 'snmpset' case above) when 'snmpset' is used. Oddly, in the override case I do see an associated get ('snmpget') return the proper override (enable) value:

snmpget -v2c -c private -m ALL localhost IF-MIB::ifLinkUpDownTrapEnable.4
IF-MIB::ifLinkUpDownTrapEnable.4 = INTEGER: enabled(1)

Moreover, whenever the override is used (note the use of the '-rw' token) I do not see any of the normal table access methods in ifXTable.c get called (i.e., no breaks in ifLinkUpDownTrapEnable_{get|set}). Why is this? And why does this have an effect on the ultimately relevant conditional in _check_interface_entry_for_updates()?

My preference is to use the override mechanism so that I can persist (and ultimately prevent sets by removing the '-rw' token) the enable/disable state.

Thanks for any insight anyone might be able to provide.

Regards,
-David