Mapping network topography with nmap

Question

I would like to create a map of my network. Currently the layout

         Internet 
            |
          router       pc
            |          | 
  server - switch - wap/switch - router - server
            |
    pc - wap/switch - pc

I guess I could create a script that (first using nmap, and then traceroute and possibly some iperf toillustrate speeds) would interpret the topography and give me a picture of what topography I have.

nmap is the network mapper - so I assume that something like what I want is possible with nmap - but how do I go about scanning to find it out.

Currently there is only 1 subnet - 192.168.1.0/24

score 1 · Accepted Answer · answered Apr 07 '23 at 06:32

As described in nmap man page

Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services (application name and version) those hosts are offering, what operating systems (and OS versions) they are running, what type of packet filters/firewalls are in use, and dozens of other characteristics. While Nmap is commonly used for security audits, many systems and network administrators find it useful for routine tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.

So despite the name, it doesn't have the capability to create a full topology map as you describe; as David and Frank said. I can't really even envision a single command that could.

Creating a network topology map automatically requires a proper network management application which probes the network devices using SNMP. SNMP has its own little quirks.

The devices to-be-probed must have a running SNMP agent that provides the SNMP interface. By far most SoHo-devices do not - whether yours do is stated in the tech specs. Usually the agent isn't available on the end devices either, one has to install Net-SNMP, OpenSNMP or a commercial solution.

Also while SNMP is defined and standardized by IETF RFCs, the implementation is left up to the manufacturers. Thus the management application must have appropriate manufacturer MIBs loaded to interpret the responses correctly.

Unless you're interested in learning SNMP network management, in a network this size installing one is a bit of an overkill. It's by far faster and easier to just draw a topology map and maintain it manually.

Mapping network topography with nmap

1 Answers1