Upon making changes to the sysName or the DNS name of a device after it was initially discovered by NetOps Performance Management, you may notice that during rediscover of the same device this naming change is not applied to the Device Name.
It is like when a rediscover is run via a Discovery Profile, the Device Name is not re-evaluated and no update to the actual device name takes place.
The Discovery Profile have the following Naming Order:
1. Host Name
2. System Name
3. IP Address
Release: IMDAGG99000-2.6-Infrastructure Management-Data Aggregator
Hostname re-evaluation in NetOps Performance Management only applies to those devices that originally had a hostname entry in DNS when the Discovery Profile was run the first time. For all such devices, PM hostname re-evaluation feature will detect any updates to their hostname.
For devices which didn't have a DNS entry at the time of Discovery Profile being run, no hostname re-evaluation will occur, and only Discovery Profile re-running will pick up the new hostname if it is added to DNS.
Regarding devices that were not initially resolvable by DNS, for them Performance Management will use the sysName. PM will only detect the new hostname if the Discovery Profile is re-run. The re-evaluation of the sysName is not related to hostname re-evaluation.
When a device's sysName attribute changes and it's Discovery Profile is set to use sysName to name the device, the Discovery Profile needs to be re-run (or you can click "Rediscover" on an individual device) in order to pick up the new sysName and have it update the device's name.
Additional details on how Performance Management is expected to work in regards to Data Collector (DC) hostname re-evaluation upon rediscover.
When the DC starts up, it builds a list of device on that DC that are in the LifeCycle active state. Then all Mediation Manager devices and VM's are filtered out from this list to exclude them from hostname lookup. The remaining list of devices is used by the hostname re-evaluation process.
If current hostname is empty or null, then hostname lookup will not be re-evaluated. This final count of filtered devices is also printed out.
Note: by default, there could be a delay of up to two days before the new hostname of a device is reflected after DC restart. We purposely distribute the hostname lookups for devices randomly over the entire period of hostname re-evaluation and throttle the requests to the DNS servers to avoid hit them all at once and possibly cause failure due to poor performance.
Currently we don't support any on-demand mechanism to re-evaluate the hostname.
When performing hostname lookups, we use the default DNS servers configured on the DC machine. This is whatever is configured in the Operating System - by default what nslookup will return. We don't allow the specification of a custom DNS server from the IP Domain; even though this entry may appear in the NetOps Portal, it is not used by the DC during hostname lookup.