Summary of differences between 2.2 and 2.0.

• In 2.0 you could compile tunnel device into kernel and got set of 4 devices tunl0 ... tunl3 or, alternatively, compile it as module and load new module for each new tunnel. Also, module ipip was necessary to receive tunneled packets.

  2.2 has one module ipip. Loading it you get base tunnel device tunl0 and another tunnels may be created with command ip tunnel add. These new devices may have arbitrary names.

• In 2.0 you set remote tunnel endpoint address with the command ifconfig ... pointopoint A.

  In 2.2 this command has the same semantics on all the interfaces, namely it sets not tunnel endpoint, but address of peering host, which is directly reachable via this tunnel, rather than via Internet. Actual tunnel endpoint address A should be set with ip tunnel add ... remote A.

• In 2.0 you create tunnel routes with the command:

      route add -net 10.0.0.0 gw A dev tunl0
  

  2.2 interprets this command equally for all device kinds and gateway is required to be directly reachable via this tunnel, rather than via Internet. You still may use ip route add ... onlink to override this behaviour.