Notes for IPv6.

If you are using libc5, you may need to edit the Makefile so that
libinet6 is linked in and your IPv6 include files are found in the
right place.  The definitions in question are at about line 63. 

If you use glibc, you should get the latest 2.1 snapshot.  In this
case you do not need to edit the Makefile or apply any patches.
Version 2.0 of glibc has no support for IPv6.

Not all the IPv6 functionality is implemented in the kernel.  As of
2.1.51, the code to delete IPv6 routes is still missing, and these
operations will fail silently.  The code to delete IPv6 interface
addresses has been written, but not yet (again, as of 2.1.51) merged
with the mainstream kernel distribution.

You may find that you are missing files such as <netinet/ip6.h>.  This is
not a bug in net-tools; you should find some newer include files.