I would definitely try Teredo first, though it does depend on the NAT design used by your ISP (you want remote IPv4 hosts to repeatedly see the same source address after repeated connections -- if the reported address changes, Teredo won't work for you).
The protocol doesn't require explicit ISP support, though NAT design can certainly break it and ISPs can filter it if they choose. When it works, the net effect is that any two hosts running Teredo clients can connect to each other via their client's IPv6 addresses, even if an IPv4 network sits between them.
Under the hood, it tunnels on top of NAT'd UDP over IPv4, using a 3rd party public IPv4 server to mediate the connection start-up (needed for NAT busting) -- but all of that is transparently handled by the Teredo client, so using it seems exactly the same as connecting to any other IPv6 host. There's a small privacy aspect present since that other server sees your source and destination trying to start a connection, but all the real traffic is direct, peer-to-peer.
Since the effect is to allow connections despite a NAT, you should make sure you are suitably firewalled, patched up, hardened, etc. Some teredo clients may also require you to explicitly enable in-bound connections on the interface.
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I would definitely try Teredo first, though it does depend on the NAT design used by your ISP (you want remote IPv4 hosts to repeatedly see the same source address after repeated connections -- if the reported address changes, Teredo won't work for you).
The protocol doesn't require explicit ISP support, though NAT design can certainly break it and ISPs can filter it if they choose. When it works, the net effect is that any two hosts running Teredo clients can connect to each other via their client's IPv6 addresses, even if an IPv4 network sits between them.
Under the hood, it tunnels on top of NAT'd UDP over IPv4, using a 3rd party public IPv4 server to mediate the connection start-up (needed for NAT busting) -- but all of that is transparently handled by the Teredo client, so using it seems exactly the same as connecting to any other IPv6 host. There's a small privacy aspect present since that other server sees your source and destination trying to start a connection, but all the real traffic is direct, peer-to-peer.
Since the effect is to allow connections despite a NAT, you should make sure you are suitably firewalled, patched up, hardened, etc. Some teredo clients may also require you to explicitly enable in-bound connections on the interface.