THINK about it...

00:60:12:12:14:34

is a valid MAC.  Is it local or remote?  How do you tell?  You can't...

Is it the MAC of the destination, the source or some intermediate hop?  You
can't tell unless you know the network topology.

IP addresses are self-referential, because you have the netmask to divide
into host and network portions, which you then compare to your own interface
(or a list of host/mask via -m).

With MAC addressing you have non of that.  Just 48 bits


-----Burton


-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of
Schoplocher Peter (Student at Congleton)
Sent: Friday, September 12, 2003 12:49 PM
To: '[EMAIL PROTECTED]'
Subject: [Ntop] --local-subnets & --no-mac


Hello Everybody,

short version:
is there a way to make ntop trust only IP addresses but display MAC
addresses "as if started w/o -o" ?

long version:
I use ntop to monitor large networks via switches (port mirroring). If I
don't use -m, everything "works fine", but as expected most of the traffic
is considered remote<->remote.
However if I tell ntop what to consider local, it stops picking up all hosts
(I am not sure about remote hosts, but it definitely fails to see several
local hosts; I monitored the exact same traffic using two different ntop
sensors connected to a hub, one with -m and one without). One of the local
hosts ntop actually displays, seems to produce much more traffic then it
actually does and the number of open ports is not correct either. Naturally,
the displayed MAC is in fact the gateway's (and the traffic is probably the
total traffic coming through that gateway, so that the open ports mentioned
above are probably indeed open, but on several different hosts).
If I add -o, everything "works fine" again, ntop (most probably) picks up
all hosts and classifies them remote/local according to -m. But it does not
only not "trust MAC addresses" [manpage] but also it does not diplay them...
Eventually, that is still pretty good.
But I don't understand why distinguishing between local and remote traffic
inhibits the monitoring of MAC addresses (and IPX). In case this isn't due
to my settings or a bug, I would also welcome a way of just displaying the
MAC addresses ntop figured out in a separate table row.

Thanks in advance!
Regards
Peter
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