FC3: IPv6 Route add failed; ping6 not working

[Eder Norbert]

Hello all,
 
I have a Fedora Core 3 PC with a IPv6 Address.
I will ping now a IPv6 address in a other Segment/VLAN, so I must add a
route.
But this fails with "RTNETLINK answers: Invalid argument" or "Error:
either "to" is duplicate, or "gw" is a garbage."
 
I tried following commands:
ip -6 route add '16::/16'  via  51::f:1 dev eth0
ip -6 route add '16::/16'  via  51::f:1 
ip -6 route add '16::/16'  gw  51::f:1 dev eth0
ip -6 route add '16::/16'  gw  51::f:1 
 
 
With 
ip -6 route add '16::/16'   dev eth0  
it is working, but when I make 
ping6 16::f:1
he always used the loop-back Interface and not the eth0.
 
Do you know, were the problem is??
 
 
Thanks.
bye,
Nobsi