>>There are some lines in basesrc/usr.sbin/pppd/pppd/Makefile version 1.27:
>>CPPFLAGS+= -DCBCP_SUPPORT -DCHAPMS -DUSE_CRYPT -DMSLANMAN
>>CPPFLAGS+= -DINET6
>(snip)
>>Building with the CPPFLAGS+= -DINET6 works OK.  I think
>>the Makefile should be updated to check for USE_INET6.
>	USE_INET6 is only for pkgsrc.  since we ship userland in binary form,
>	we need to always enable IPv6 for userland (otherwise, users would
>	need to recompile the whole userland when he turns on IPv6).
>	I'll fix non-IPv6 build anyways.  sorry for the mess.

	aha, you did not clean the directory and old eui64.o was there.
	perform "make clean" and you will be fine.
	(there should be a way for make to detect Makefile changes...)

itojun