Apache service on App Server 1 is not reachable from LB host
Which means you didn’t add the correct rules in Iptable to open Apache access for LB host (as asked in the question) even though Apache service was up but if correct rules weren’t added then it won’t be reachable from LB host.
In general, AFAIK, iptables save will save the existing rules in a text file, that you must manually load during boot or on every service restart. In Red Hat based distros however, you can edit /etc/sysconfig/iptables file and reload(or restart) the respective systemd service with systemctl reload iptables.
Dropping the traffic is redundant since you specified the source IP in the ACCEPT statement. It would be necessary if the ACCEPT statement was broader and needed to limit it, eg: ACCEPT an entire subnet and DROP a couple of hosts.
I have used the commands as follows
sudo yum install iptables-services -y
sudo systemctl start iptables
sudo systemctl enable iptables
iptables -A INPUT -p tcp --destination-port 8083 -s 172.16.238.14 -j ACCEPT
iptables -A INPUT -p tcp --destination-port 8083 -j DROP
sudo service iptables save
Notice that your command comes after the reject action , therefore all traffic blocked except ssh traffic. This is the most tricky question in sysadmins tasks. Hint: don’t use -A flag in this task