[CentOS] how to find unknown ip address?

Tue May 28 11:05:35 UTC 2013
Barry Brimer <lists at brimer.org>

>> hadi motamedi <motamedi24 at gmail.com> wrote:
>>> 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) ?
>> Listen with wireshark looking for things that don't belong.

> Thank you for your reply. So you mean it is independent of my centos
> server ip address range or it just shows the ip addresses in the range
> of my centos self ip address? (as I don't have a priori information
> about that remote node unknown ip address)

Wireshark listens to packets on the network interface you tell it to use. 
It doesn't have to be in the same IP range because it listens at a lower 
level than TCP/IP.  For that matter, it will see other protocols that are 
present as well.