Cisco Discovery Protocol (CDP) is a nice feature, similar to the standard Link Layer Discovery Protocol (LLDP), for discovering how devices are interconnected at the data link network layer -- or directly wired between devices, in plain English. CiscoWorks does a very good job discover devices on a network using CDP and other protocols. The way it is done is: (1) A protocol or a set of protocols are selected; (2) A set of seed devices are configured for each protocol; (3) A job is scheduled to run periodically to sweep the network.
We are pretty much a Cisco shop, so I select CDP and routing table, give them the core routers as seed devices, and set it to run every some days of the week. The job usually takes a long time due to the number of devices involved -- One could exclude devices by rules, such as IP address range or device classification (sysObjectID), etc. which would save time for the job as it avoids querying devices that may never respond.
The mystery I run into is that, my scheduled discovery job runs but never seems to be able to completely finish. CiscoWorks always tells me that it does not have any information for the latest discovery job. Cisco TAC engineers have provided suggestions, but nothing seems to help.
After some digging around, I found that the log rotation job I scheduled to run everyday is likely the culprit. I may have inadvertently checked the Restart Daemon Manager option when scheduling the log rotation job.
The lesson for me is, with Cisco's software, I have to be aware what I am doing every step of the way to avoid shooting myself in the foot. Otherwise, I may be in for a fun ride that is hard to find a way out.
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