So I had the need to monitor latency with Radius.
I added the necessary text into the Probe section and restarted Smokeping to see an error.
[....] Starting latency logger daemon: smokepingrequire Smokeping::probes::Radius failed: Can't locate Authen/Radius.pm in @INC (@INC contains: .. /usr/sbin/../lib /usr/sbin/../thirdparty/lib/perl5 /etc/perl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.14 /usr/share/perl/5.14 /usr/local/lib/site_perl .) at /usr/share/perl5/Smokeping/probes/Radius.pm line 19, <File> line 7. BEGIN failed--compilation aborted at /usr/share/perl5/Smokeping/probes/Radius.pm line 19, <File> line 7. Compilation failed in require at (eval 20) line 2, <File> line 7.
Just do apt-get install libauthen-radius-perl
There is also libnet-dns-perl, libnet-ldap-perl, and libnet-telnet-perl. These are useful for the other probe types.