Website is not accessible when firewall is enabled: Site can't be reached

Symptoms

RHEL7/CentOS 7 is used.

New IP address is pointed to website, but it is not accessible:

CONFIG_TEXT: Site can't be reached

Curl utility shown the following:

# curl -I http://example.com -v
* About to connect() to example.com port 80 ( #0 )
*  Trying 203.0.113.2... No route to host
* couldn't connect to host
* Closing connection #0
curl: (7) couldn't connect to host

2. Traceroute utility shows the following:

# traceroute -T -p 80 example.com
traceroute to example.com (203.0.113.2), 30 hops max, 60 byte packets
1  gw4.example2.com (1.1.1.1)  0.211 ms  0.204 ms  0.250 ms
2  nsl-example3.com (2.2.2.2)  0.524 ms  0.369 ms  0.509 ms
16  * * *
17  * * *
18  * * *
19  * * web18.example4.com (3.3.3.3)  302.789 ms !X <-------- "communication administratively prohibited"

The following services are allowed on local firewall:

# firewall-cmd --list-services
ssh dhcpv6-client

Cause

Local firewall blocks connections to HTTP service.

Resolution

1. Login to the server over SSH

2. Allow HTTP service:

# firewall-cmd --permanent --add-service=http
success
# firewall-cmd --reload
success
# firewall-cmd --list-services
ssh dhcpv6-client http