Verified on CFME-5.6.2.0.20160913114355_70e9086
When entering wrong IP address, the validate operation is processed for several min, and eventually no error is displayed on UI.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHSA-2016-1996.html