There are several groups of IP addresses that, by design, do not route on the internet 10.x.x.x - 127.x.x.x - 192.x.x.x are some of those... some folks have devices that do NAT (Network Address Translation) which maintain the reserved addresses on the private side of the connection but use a valid IP on the public side... Netgear and Linksys are two manufacturers of such devices. These offer some firewall properties but are not true firewalls. Having one of these devices can create an issue with the owners' ability to upload to others. As one user stated they can work through the device by using port forwarding. In other cases where the end user cannot control the firewall actions, like on a business or campus LAN several P2P clients offer the ability to use a method referred to as a 'Push'. This is where a request is passed back to the firewalled user and the firewalled client initiates the upload as opposed to the other way around... Pushing the upload rather than responding directly. Real firewalls often have a trusted side (the private side) and a non-trusted side... non-trusted (the public side) are not allowed to open a port for activity... but the internal user can sometimes do so. I know Shareaza supports pushing and I am certain others do too but I am not sure about Limewire.