adding secondary IP interface and IP index number to APA

just put the IP in netconf using the Physical PPA lan port (like normal), then when APA starts, it will bind it to the APA port
INTERFACE_NAME[1]=lan0:1
IP_ADDRESS[1]=1.2.3.4
SUBNET_MASK[1]=255.0.0.0
INTERFACE_STATE[1]=up

if adding a secondary IP once APA is already running: bind it to the APA PPA (lan900)  as follows:
ifconfig lan900:1 1.2.3.4 255.0.0.0 up

HPUX routing and the ip_strong_es_model network tunable

A "graypaper" on  understanding HP-UX routing including details on ip_strong_es_model tunable: http://www.mayoxide.com/presentations/Understanding_hpux_routing.pdf

Best description of the ip_strong_es_model tunable via this ITRC link: http://forums11.itrc.hp.com/service/forums/questionanswer.do?admit=109447626+1267461248860+28353475&threadId=1126880
ip_strong_es_model is used when you want to configure multiple, physical NICs in the same IP subnet, and/or want the functional equivalent of per-source IP routes.