Enterprise Manager: Hostname should not contain underscore _ in it.

While using dbca to create a database with Enterprise manager configured. The configuration of the Enterprise Manager failed with the following error message:

"Invalid Hostname isvp14_ora. Hostname should not contain an underscore _ in it."

 Well, RFC 952 and RFC 1123 explain the rules for choosing a hostname.

Anyroad, here is the workaround:
On the shell prompt set the ORACLE_HOSTNAME variable to your machines IP address, and then re-configure.

bash-3.2$ export ORACLE_HOSTNAME=<ip_address>