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+To be able to set up the VPN, at least one node needs to be reachable by an
+unchanging address of hostname. This is normally not the case with common
+DSL uplinks (they change addresses every day).
+To mitigate this problem and get a fixed hostname, there are services called
+dynamic DNS or short DDNS. There are lots of [different DDNS services][1], some
+are free, some cost money.
+Most of those services provide a common API that can be used by freely available
+tools to update the address whenever it changes. Mainstream DSL routers have
+built-in clients for this API so nothing has to be installed to set up DDNS.
+
+Besides this unchanging address, a port has to be opened for VpnCloud. This has
+to be done in the settings of the DSL router. The default port for VpnCloud
+is 3210. This process is different for every router but it usually can be found
+under the name of "Port forwarding" or "Exposed ports" (not "exposed host").
+
+[1]: http://dnslookup.me/dynamic-dns/
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