Bizarre IPv6 problem

[Edward Lilley]

I'm having a rather odd issue with IPv6 here.
This is my setup:

[computers in LAN] -- [router] -- [rest of IPv6 internet]

The router knows my IPv6-subnet, and assigns all he computers a
globally-unique IPv6 address, and all computers in the LAN can talk to
each other and to the router over IPv6. That's all working fine.

The only problem is, a computer in the LAN can only connect to an IPv6
host beyond the router (e.g. ipv6.google.com) if it is constantly
maintaining a connection to the router itself -- otherwise
"ping6 ipv6.google.com" just hangs indefinitely. So if I run
"ping6 <routerhostname>" I can then do ping6, HTTP over IPv6, &c. to
sites like ipv6.google.com with no problems. (at the moment I just leave
"ping6 <routername> &" running in the background all the time).

This only seems to effects gnu/linux boxes on the lan (ubuntu & fedora),
not WinXP ones which have had IPv6 enabled.

I suspect it is some weird IP-related sysctl setting that I haven't
found yet, but it's somewhat strange. Any thoughts on how to resolve it
without the kludgy ping6-in-background hack?

Thanks in advance for any suggestions,
Edward Lilley