Hi Ghofran Samir,
I recommend you to use DNS for FQDN, But If not, you can still installing Portal for ArcGIS by giving hostname alias of IP Address in host file.
Edit the /etc/hosts file
The /etc/hosts file must contain a specific entry for Portal ArcGIS. This entry should be separate from the localhost entry, and its own line in the hosts file. The entry should have the following format:
<IP address> <machine name> <fully qualified domain name>
For example, 192.168.11 fatahmachine fatahmachine.esrisa.com
Hopefully, it helps you and what you are looking for, brother.
Thank you,