How does Nectus discover your network?


During Nectus installation user can define up to 10 IPv4 subnets that will be used

as initial seed subnets for ICMP scan. Immediately after Installation is completed Nectus

starts ICMP scan of provided subnets and builds a list of live IP addresses that responded to Ping.

For all the IP addresses that responded to Ping Nectus attempts basic SNMP discovery for sysObjectID

with Read-Only credentials provided during installation.

Nectus Supports SNMP v2c and V3 with (DES, 3DES, AES128/192/256) Ciphers.

If IP address responds to sysObjectID SNMP query Nectus will perform additional SNMP queries

that may be specific to different hardware platforms.  Nectus collects device hostnames,

list of interfaces, interface names, IP addresses, content of IP routing and MAC forwarding tables etc.


Additionaly during basic discovery Nectus reads devices’ CDP tables and uses CDP information to

find connected devices. CDP information allows Nectus to build table of interconnections,

visualize network topologies and allows Nectus to expand scope of discovery beyond initial 10 subnets.


If network has CDP enabled on all interfaces then Nectus can normally discover 100% of the devices even

if initially configured seed subnets do not cover whole allocated address space that is used.


In ideal cases specifying only single IP address (/32) during installation is sufficient to perform

complete network discovery.

Very often we see Nectus installations configured with as single seed subnet.

This is normally works fine for very large environments but in smaller networks it may result in

increased CPU utilization on some older routers that responsible for generating “ICMP Host Unreachible” messages for

IP addressed that are not in the IGP routing table as Nectus generates pretty large amount of ICMP traffic during ICMP scan phase.