Use the "ifconfig" command to define internal IP-addresses for both ends of a tunnel "0" as addresses for an interface denoted as "tun0".
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ifconfig tun0 1.1.1.1 1.1.1.2 |
The tun command defines real IP-addresses for the tunnel "0" extremities.
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tun 0 src 195.23.23.23 dst 194.34.34.34 |
Outgoing packets are encapsulated into IP datagrams and sent to the "194.34.34.34" address.
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The "194.34.34.34" address shall also be attainable through an interface of the router different from that used to access the tunnel. This can be done, for example, by using explicit static routing (the route add command), or by prohibiting importation of some of the RIP protocol route descriptors arriving to that interface. If this condition is not satisfied, a looping may happen, when already encapsulated packets come back to the tunnel entrance, and so on, causing system overload. The system watches over such situations, and when discovering a loop, drops erroneous packets and writes a message into the system log. | Code Block |
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| tunX: looping... |
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The "195.23.23.23" address is inserted into the datagram as source address.
The "195.23.23.23" address must be a real IP-address for one of the router's interfaces; for the same reason, it shall be attainable from the router at the tunnel's remote end through the existing network (and not only through this tunnel).