[CentOS] how to find unknown ip address?

Tue May 28 05:03:34 UTC 2013
hadi motamedi <motamedi24 at gmail.com>

Dear All
On my network, there is a node with unknown ip address so I do not
know about its range and it can be any of the range xx.xx.xx.xx . Is
there any tool on my centos server to find this unknown ip address
(irrespective of the range of my centos server self ip range) ?
Thank you