25. 04. 2012
NeDi – Network Discovery that Really Works
When networks begin to grow admins begin to loose overview. NeDi efficiently searches and documents a network. This makes it an ideal starter for any management system that builds on top.
One of NeDi`s distinct features is its capabilitiy to draw network topologies very efficiently. Network discovery usually means scanning all network addresses for hosts and their services. This doesn’t scale well in large networks and is completely foredoomed in IPv6 networks.
NeDi takes a different road. It only queries a few seed devices for other devices they know. This may take place either by quering ARP or routing tables, but the smartest approach is to use layer 2 neighbourhood discovery protocols such as CDP or LLDP. Any devices identified by this procedure are memorized by NeDi in a table of yet to be queried devices. nedi works its way down the table until there are no more devices left and so recursively creates a topology of the net.
NeDi uses SNMP to query the devices. That’s why nedi needs access to these devices. Setting up SNMP options is part of an admins job when NeDi is configured intitially. But there’s more to nedi than simply quering for network neighborhood. While at it, it may also collect any other useful information, such as VLANs, connected end devices, CPU load, temperature, interface throughput, modules including their serial numbers etc. pp.
After only one, initial scan NeDi is able to draw a complete picture of a networks topology, making it one of its highlights. It is impressive to get such a detailed overview over your own network. Filters aid to focus in case NeDi turns up to many details. NeDi stores all data in a database. The database is accessed from NeDi’s reports. All known hosts are available via mouse click including how many ports are still available and on which ports there have been too many errors. That makes NeDi an ideal foundation for asset management systems. NeDi lists everything on network that actually exists. It remains an admins job to filter this for what should be on the network. Discovering when an GBIC has been replaced becomes a matter of minutes. NeDi simply lists all device types and operating systems on mouse click.
It also stores specific operational parameters in RRD databases, which makes it easy to draw graphs of memory or interface usage. Graphing troughput becomes especially meaningful the moment network overview becomes part of the picture.
In case an SNMP agents sysLocation has been set in a form nedi can handle it may even generate topographic maps or display them using Google Maps. But nedi also offers features for network monitoring. If a monitored parameter exceeds a limit, nedi may send an admin alarm. Mail notifications may be sent when a new device shows up, something has become to hot or when nedi has discovered too many errors on a line.
As customary for open source software nedi may be adjusted to ones own needs. Its relatively easy to model new devices. nedi can work with arbitrary devices as long as they speak SNMP. Equipped with all this network knowledge its simple for an admin to keep overview and react on events in time.
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