Hello,
There is a Cisco bug : CSCuz64174 / PI 3.x - Missing links in topology with latest DP 4/5.
Symptom:
links between devices are randomly missing.
Conditions:
The DP will cause links to be not detected for devices discovered AFTER applying DP4 or DP5 on a 3.0 System that does not have TechPack installed
The solution is to install Device Pack 6.0 or to use the workaround.
For me, the installation of DP6 not resolve my problem but you can try.
source : https://bst.cloudapps.cisco.com/bugsearch/bug/CSCuz64174/?referring_site=bugquickviewredir
source : http://www.cisco.com/c/dam/en/us/td/docs/net_mgmt/prime/infrastructure/3-0/release/notes/pi30-device-pack6-readme.pdf