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Re: [LUG] Tools to map a network

 

Rob Beard wrote:
>
> I'm in the process of trying to create a network diagram for a network
> which looks like a tin of spaghetti.  Now some of the switches connected
> to this network are managed and give me some details about the network
> (although not much that I can decipher).  I believe there are a couple
> of 10MBit hubs on this network too which I'm guessing is causing a bit
> of a bottleneck.

What you want is "network discovery"  I think (at least before Microsoft
borrowed the term to make searching for it harder).

I don't use any such tools routinely and haven't used them
professionally on Linux (unless you count firewall installation),
although "nmap" and "ntop" both impinge on the area somewhat, in that
they tell me what the devices on my network are (when I forget and
haven't kept the documentation upto date).

A lot depends in the network topology.

I've not seen these tools discover dumb hubs, or report ethernet rates
on remote segments. I'd guess you can't do those things on remote
segments unless the switch can report it, although specialist network
equipment or active testing might be able to guess some of these things,
but probably not without swamping all available bandwidth (which may not
be ideal). i.e. If a whole chunk of devices are 10Mbps even though the
MAC address is for a 10/100 or 10/100/1000 card you can assume hubs
exist and the switch may tell you from what port they are connected.

I've not tried "etherape", "cheops" or "cheop-ng". cheops & cheops-ng
look to be dead but cheops is packaged in Debian. However I wouldn't be
surprised if even quite old tools work reasonably well. WiFi has kind of
complicated Ethernet, but not that much.

Most of the network management tools like netdisco supply you with some
discovery tools, and will poll for information from switches. So it
might be appropriate to roll out one of those for use, rather than map
it now and hope it doesn't change too much. Please print out what you
discover and details of any tools installed and tape it to a suitable
cabinet for the next techie - it may save them a lot of time.

Also if you have a spare switch, you could sequentially replace any hubs
you find, and document what it reports. Then you'd know which were worth
replacing.


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