Subscription-manager registration fails with “[Errno 110] Connection timed out” when registering system to customer portal

Issue

• System registration failing with [Errno 110] Connection timed out error.
• While registering the system to the customer portal using subscription-manager register command, it fails with the below error:

# subscription-manager register --username "xxxxxx"--password  "xxxxxxxx" 
Registering to: subscription.rhsm.redhat.com:443/subscription
Network error, unable to connect to server. Please see /var/log/rhsm/rhsm.log for more information.