we have a test case from the operator that upon expiry of router lifetime the client device supposed to send Router solicitation message to the router. But this is not happening. is this because of some kernel configuration missing ? what could be the reason for this? Usually the router life time is infinite but for this particular test case it is of very low value of 240Seconds.Please help me.
Take a look at RFC 4861: Router Solicitations should only be sent when connecting to a link. After that the host just listens to the periodic Router Advertisements sent by the router.
If something goes wrong this is the router's fault for not sending a new RA in time, not the host's.