Can someone provide some granular detail on exactly how the Cisco Network Collector retrieves information about network devices (for purpose of inventory assessment)? One of our customers is interested but want's information on exactly how it works and how it will impact their network during the discovery process.
Hope this helps:
Simply stated, it doesn't. During network discovery, CNAC uses an almost immeasurable amount of network bandwidth. CNAC's discovery method (ICMP Ping) sends one small (< 300 byte) ICMP packet per IP address. In addition, CNAC breaks up large IP address ranges into blocks of ~20 addresses and waits several seconds for responses from those 20 addresses. By searching the network in this way, CNAC should have no noticeable affect on your network bandwidth or devices. For those IP Addresses that respond to the ICMP Ping, CNAC sends small (<300 byte) UDP packets until the user defined number of SNMP Strings and Retries has been reached or CNAC was able to establish an SNMP connection, whichever occurs first. The only other network traffic potentially generated by CNAC occurs after a successful SNMP read only string connection to a discovered IP Address, and this traffic is also trivial. a small UDP Packet (<300 bytes) is transmitted to the device, requesting the industry standard SNMP sysObjectID value for manufacturer and model. NOTE: CNAC 1.X includes a bug whereby a Telnet connection is attempted during discovery for the purposes of confirming the proper Telnet credentials, which would be used during the Intelligent Inventory function. This bug is worked around by simply not entering any CLI Credentials during initial configuration of CNAC, and entering these credentials instead prior to the Intelligent Inventory function.