IPIP tunnel behind NAT

[Steve Bertrand]

Hi everyone,

I'm trying to configure a GIF IPIP tunnel from a FreeBSD box to a Cisco 
router in order to route IPv6 blocks to a remote location.

However, I can't find good documentation to find out whether this will 
work in behind a NAT device.

The FreeBSD box has a private IP, NAT'd 1:1. The Cisco is across the 
'net and is in the public network.

Will this tunnel setup work? If so, how? Will I have to move the FreeBSD 
box outside of NAT and give it a public IP?

Regards,

Steve