Use @@lib@@ instead of hardcoded lib, for lib64 systems. Patch should
be pushed upstream.

diff -cr mrtg-2.16.4.lib64/bin/cfgmaker mrtg-2.16.4/bin/cfgmaker
*** mrtg-2.16.4.lib64/bin/cfgmaker	Mon May 17 09:59:20 2010
--- mrtg-2.16.4/bin/cfgmaker	Sun Jul 11 14:58:42 2010
***************
*** 44,50 ****
  
  use FindBin;
  use lib "${FindBin::Bin}";
! use lib "${FindBin::Bin}${main::SL}..${main::SL}lib${main::SL}mrtg2";
  
  use MRTG_lib "2.100015";
  use Getopt::Long;
--- 44,50 ----
  
  use FindBin;
  use lib "${FindBin::Bin}";
! use lib "${FindBin::Bin}${main::SL}..${main::SL}@@lib@@${main::SL}mrtg2";
  
  use MRTG_lib "2.100015";
  use Getopt::Long;
diff -cr mrtg-2.16.4.lib64/bin/indexmaker mrtg-2.16.4/bin/indexmaker
*** mrtg-2.16.4.lib64/bin/indexmaker	Mon May 17 09:59:20 2010
--- mrtg-2.16.4/bin/indexmaker	Sun Jul 11 14:58:28 2010
***************
*** 48,54 ****
  
  use FindBin;
  use lib "${FindBin::Bin}";
! use lib "${FindBin::Bin}${main::SL}..${main::SL}lib${main::SL}mrtg2";
  
  use MRTG_lib "2.100016";
  use Getopt::Long;
--- 48,54 ----
  
  use FindBin;
  use lib "${FindBin::Bin}";
! use lib "${FindBin::Bin}${main::SL}..${main::SL}@@lib@@${main::SL}mrtg2";
  
  use MRTG_lib "2.100016";
  use Getopt::Long;
diff -cr mrtg-2.16.4.lib64/bin/mrtg mrtg-2.16.4/bin/mrtg
*** mrtg-2.16.4.lib64/bin/mrtg	Mon May 17 09:59:20 2010
--- mrtg-2.16.4/bin/mrtg	Sun Jul 11 14:58:54 2010
***************
*** 81,87 ****
  
  use FindBin;
  use lib "${FindBin::Bin}";
! use lib "${FindBin::Bin}${main::SL}..${main::SL}lib${main::SL}mrtg2";
  use Getopt::Long;
  use Math::BigFloat;
  
--- 81,87 ----
  
  use FindBin;
  use lib "${FindBin::Bin}";
! use lib "${FindBin::Bin}${main::SL}..${main::SL}@@lib@@${main::SL}mrtg2";
  use Getopt::Long;
  use Math::BigFloat;
  
diff -cr mrtg-2.16.4.lib64/bin/mrtg-traffic-sum mrtg-2.16.4/bin/mrtg-traffic-sum
*** mrtg-2.16.4.lib64/bin/mrtg-traffic-sum	Mon Dec 28 02:53:16 2009
--- mrtg-2.16.4/bin/mrtg-traffic-sum	Sun Jul 11 14:59:04 2010
***************
*** 33,39 ****
  
  use FindBin;
  use lib "${FindBin::Bin}";
! use lib "${FindBin::Bin}${main::SL}..${main::SL}lib${main::SL}mrtg2";
  use MRTG_lib "2.090017";
  use POSIX qw(mktime);
  
--- 33,39 ----
  
  use FindBin;
  use lib "${FindBin::Bin}";
! use lib "${FindBin::Bin}${main::SL}..${main::SL}@@lib@@${main::SL}mrtg2";
  use MRTG_lib "2.090017";
  use POSIX qw(mktime);
  
diff -cr mrtg-2.16.4.lib64/contrib/cfgmaker_dlci/cfgmaker_dlci mrtg-2.16.4/contrib/cfgmaker_dlci/cfgmaker_dlci
*** mrtg-2.16.4.lib64/contrib/cfgmaker_dlci/cfgmaker_dlci	Tue Feb 26 05:16:39 2002
--- mrtg-2.16.4/contrib/cfgmaker_dlci/cfgmaker_dlci	Sun Jul 11 14:59:12 2010
***************
*** 36,42 ****
  
  use FindBin;
  use lib "${FindBin::Bin}";
! use lib "${FindBin::Bin}${main::SL}..${main::SL}lib${main::SL}mrtg2";
  
  use BER "0.57";
  use SNMP_Session "0.59";
--- 36,42 ----
  
  use FindBin;
  use lib "${FindBin::Bin}";
! use lib "${FindBin::Bin}${main::SL}..${main::SL}@@lib@@${main::SL}mrtg2";
  
  use BER "0.57";
  use SNMP_Session "0.59";