(usagi-users 03799) MIPv6 tunnel over PPP

We are running kernel 2.6 and are running MIPv6 (MIPL) for over PPP. 
When we try to do handoff between from one subnet to another subnet, we 
cannot bring down the PPP interface. Has anybody tried PPP over MIPv6 
and has actually moved between two PPP networks?

Thanks
Ashutosh