Why hostname command display (none) in RHEL6?

Issue

While adding ipV6 address after rebooting manually due to network failure, hostname become (none) in terminal as below when running hostname command after connecting console.

[root@(none) ~ ] #

And also, either tar and traceroute command such as binary commands in net-tools rpm packages is also not executed normally.
In addition, sftp connection was not available through ssh port 22.