doubts about my IPv6 network

["Christian Pinedo zamalloa" <christian.pinedo.zamalloa@gmail.com>]

hello,

i want to discuss with you some doubts about the IPv6 connection that
i configured in my work. The architecture is shown in the next
graphic:


                                       _____________
                                      |                      |
IPv6 1 connection <----- | ROUTER IPv6 | ------> IPv6 2 connection
                                      |                      |
                                      -------------------
                                                  |
                                                  |
                                                  v
                                               My LAN

The router has two connections to the IPv6 world. We have two global
IPv6 prefixes of 64 bits one for each connection/interface.

So from the router router advertisement messages could be sent
announcing two global prefixes to the LAN. The computers of my LAN
could have two global addresses, so the PC is the responsible of
selecting one of these global address as origin address for outgoing
packages. Then the router should select the output to the IPv6
network. If he selects the bad interface the package would be reject
by the firewall of the ISP because the package has an incorrect origin
address.

The router could change IPv6 routing preferences and the PC should
know which IPv6 address use as origin address. Is this possible to
announce in router advertisement messages? Am I completely lost? xD

Thanks,

--
Christian Pinedo Zamalloa