Abnormal behaviour of ping6

[Sharmila <shard@intoto.com>]

Hi all,
		I am a new user of Ipv6 and I am using the following simple setup:
Host1------Router--------Host2
Host1,Host2 & router are linux(kernel version 2.4.18-4 ) pcs with ipv6 
insmoded .(Dual Stack is present  on all 3 m/cs).On router,I have enabled 
forwarding.

The ipv6 addresses are as follows:

host1 eth0  =   fec0::e2d2:50:fcb2:7251 / 80
router eth0  =   fec0::e2d2:50:fcb1:de7b / 80
router eth1  =   fec0::a4b4:11:111b:9dd3 / 80
host2 eth0   =  fec0::a4b4:50:fcb2:4574 / 80

Added corresponding routes on host1 and host2

Now the problem is , ping6 from host1 to host2 is successful sometimes and 
failure sometimes.In case of failure,it gives "Destination not 
reachable:Address unreachable" message.

Why is it behaving abnormally?? Am I missing some configuration ? Or is the 
problem with my m/cs?
Also, are there are any better test tools?? Please help me in this regard.

Thanks in advance,
Sharmila