I am trying to understand why one would configure a gre/gif tunnel
with encapsulation destination equal to the point-to-point destination.
E.g., on this interface, the encap destination, 10.0.0.2, is the same
as the point-to-point destination:

gre5006: flags=d051<UP,POINTOPOINT,RUNNING,LINK0,MULTICAST> mtu 1476
        tunnel inet 10.0.0.1 --> 10.0.0.2
        inet 10.0.0.3 -> 10.0.0.2 netmask 0xffffffff
        inet6 fe80::a00:20ff:fef9:60ee%gre5006 ->  prefixlen 64 scopeid 0x112d

To support this configuration, an author resorted to some cleverness that
it will be *tremendously* difficult to replicate in the New Model GRE,
which I intend both to simplify GRE, to support IPv6 encapsulation,
and to repair a bug in route caching[1].

Can anybody explain, what is use such a configuration as above?  Is there
no other way to create a similar network?

Dave

[1] The bug I have in mind has the same flavor as the one in kern/3508.

-- 
David Young             OJC Technologies
dyoung@ojctech.com      Urbana, IL * (217) 278-3933