I've seen this on our network in recent months also. It ususally has to
do with virtual machines that default to using 192.168.x.x (VMware) and
10.211.55.x (Parallels) addresses. They either exit their physical
machine not properly NATed for your network, or when they interact with
some applications, such as MS Exchange, the Exchange server may try to
reply to the original 192.168.x.x or 10.211.55.x address. Apparently
this original source address must be buried somewhere in the data
portion of the packet. Either problem makes the origin very difficult
to trace, because you can't route to, or ping, that source address.

Frank

-----Original Message-----
From: firewall-wizards-bounces@listserv.cybertrust.com
[mailto:firewall-wizards-bounces@listserv.cybertrust.com] On Behalf Of
desant1@tin.it
Sent: Sunday, November 25, 2007 9:42 AM
To: firewall-wizards@listserv.cybertrust.com
Subject: [fw-wiz] How to find hidden host within LAN

Hi everybody
I'm using RH ES4 with iptables as gateway/firewall for my
LAN.
In the last week i notice in the iptables logs that a host within
my lan is doing a lot of traffic.
The destination/source address of the
packets and the used port suggest that this host is using peerToPeer
application (emule or similar).
The problem is that i'm not able to
identify this host within my LAN:
I can see his IP address (192.168.x.
y) and i can find his mac address througth ARP, but i can't ping it and
there is no host within my lan with this Mac address.
I can't
traceroute it.
Can someone help me to find this hidden host?
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