Troubleshooting
Problem
Care needs to be take in environments where there is no name resolution
Symptom
Entity names are constructed as expected during the initial full discovery but in subsequent partial discoveries they become IP address with unexpected prefixes. In NAT environments you may see the NAT Address Space lable prefixed to the Entity name.
Cause
Since only file name resolution is configured in this environment, you send a list of device names and IP addresses into discovery using the File Finder seed file. No DNS is performed on this list of names.. The names flow from the File Finder into the Details Agent and on through Discovery. When the entities are constructed these name are used as the value for EntityName.
However, on subsequent partial discoveries, the devices are not submitted via the File Finder. As such, a call to the hostname resolution service is made, which then refers to the /etc/hosts (by default) or whatever hosts file the system is configured to use.
If, for whatever reason, those addresses cannot be resolved in the hosts file then the name resolution fails and the IP address is used for naming the entity. In one customer's example the /etc/hosts contained the private NAT addresses for the hosts. Since ITNM was in the public space those private addresses could not be reached. As a result, the hostname resolution failed and the IP address was used to name the entity. Additionally, the address space lable was appended to the entity name according to the DetailsOrContextRetProcToAgent stitcher.
Note that the results of the initial *full* discovery were as expected since it used the hostname from the File Finder seed list. It was only subsequent discoveries where the entity name was constructed against expectation.
Environment
File Finder Seed files are used to populate the discovery. Since there is no DNS on the server where ITNM is installed only the File DNS service is enabled. By default /etc/hosts is the file used for hostname resolution.
Resolving The Problem
It is essential for hostname resolution to work successfully for EntityName to be constructed as you expect to be constructed. The IP address must be contactable. This simply means that if you seed a discovery using the File Finder then the hostname/IP address pairings in that file must be the same as the results of host name resolution on the server. If the server is using /etc/hosts then ensure that the hostname/IP address pairings in /etc/hosts match those in the File Finder seed file.
In our customer's example, the /etc/hosts could not be modified with the Public addresses and so they altered the hosts file location on the server to match that of the seed file for the File Finder.
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Document Information
Modified date:
17 June 2018
UID
swg21669713