During a security test lab I have encountered some problems to get connection up…every time I try to connect to SSH or HTTP or HTTPS hosts a “Reset by peer” occurred.
Some others testers experienced the same problem and we start to investigate the issue.
First of all we had three hosts with same mac address: aa:00:04:00:0a:04. The DHCP server assign the same IP all over the hosts…..and it’s correct due the same MAC Address !!!
So we start to check Network-Manager parameters and /etc/network/interfaces file but every config was OK. In order to finish tests we have changed our MAC Address using ifconfig command and requesting a new IP from DHCP server.
Why eth0 Mac Address was fixed on aa:00:04:00:0a:04 ??? Why Network-Manager adds other two Auto eth0 connections ?
The answer is: DECNet libraries and tools !!!!! During activities we have installed some tools with DECNet dependency.
Solution: in order to fix the MAC Address problem, click on System -> Administration -> Synaptic Package Manager.
Now search for DECNet packages and mark for Complete Removal the following packages: libdnet, libdnet-dev, dnet-common and (optionally if you have) dnet-progs.
At the end of removal process reboot your PC and checks the correct MAC address applied on eth0.