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On 16/05/10 08:54, Simon Waters wrote:
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.
Thanks Simon I'll have a look at the tools. I think I found the bottleneck, a 10Mbit hub which was attached to two Gigabit switches, so the traffic was being limited to 10Mbit. I managed to swap that out with a Gigabit switch and it seems much faster although not the full 1GBit (250MBit, so it's still a lot better than the couple of Megabits it was running at).
Rob -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html