Using CS 3.1.1 if I display total devices discovered, or reachable devices I see the hostname under the system name header. If I display devices updated to DCR I see IP addresses under the host name header. Also I don't see hostnames in device management. I can't locate a hostname using the advanced search.
Under discovery settings I have Preferred DCR display name: Hostname and Update DCR Display name: Yes
It is possible I changed those settings after the first discovery, but there have been other discoveries with those settings. Is there a way to update the DCR without too much pain?
My understanding of this:
Discovery does not necessarily resolve the System Name. With CS 3.1.1 you can get a list of the devices being discoverd by going to CS > Device and Credential > Device Discovery, then clicking on the number behind 'Total devices discovered'. The list that opens has an important column 'First Found by Module'. If 'CDP'is listed here - as it is in your case - the disco process gets the value for 'System Name' from the CDP Mib of a device. So there is no name resolution involved until now -regardless what you have configured for nameresolution in LMS.
The devices are NOT yet in DCR - this is just a list of what was discovered and by which module.
The type of nameresolution you have configured comes into play when device gets added to DCR. Then the configured mechanism is responsible for how to fill in the values for 'Display Name', 'Host Name' - and 'IP Address' as well! Because now it is determined which IP Address to use to communicate with the device (could be different then what is seen by CDP!) and how to resolve the Host Name and what to use as Display Name.
If you get the list of the devices IN DCR (or of those from Campus -Data Collection) then your settings for the name resolution have worked (... and you see what you have not expected ;-) )
Devices yet being in DCR have the value of 'System' under 'First Found by Module', so this is not a general 'First Found' but only from the point of view from the LAST disco process.
I hope this is right...
and explains why you have System Names in the Discovery List but not in the list of devices in DCR.