LAN SVN server setup

Hi,
I have set up the svn server in a home LAN network, it working well with the
machines in the LAN network.
However, the Wan IP seems dynamic, how can i let the machine does not within
the LAN network connect to the svn server.

I tried : svn://my wan ip address here/repository, and there is error said,
can not find the host. seems port forwarding can solve this, can anyone help
? how should I set up ? by the way, I am running the server on windows xp.

many thanks

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