GNMS is a free Network Management System, a tool to monitor state of network elements.
All nodes are mapped on a window. States can be discovered by service, SNMP, and custom pooling, and syslog and SNMP traps can be caught.
It's written in Ruby/Gtk, and use some command tool for finding, scanning ... Such as nmap, xprobe, ping, ip, snmpget ...
a - add an host/network
d - delete a node
p - property of a node
i - move up the selected node
k - move down the selected node
j - move left the selected node
l - move right the selected node
Just run command in root:
gem install gnms