How to Unblock SSH and FTP Access to Specific IP in Linux

Firewalls(most of them) can eitherRejectorDeny/Drop thetraffic.Rejectaction sends anICMP Port/Destination Unreachableresponse back to the source whileDrop/Denyaction sends nothing back and will silently drop the connection. Which means the firewall is blocking the traffic.

Use the following syntax you can unblock an IP (the -d options deletes the rule from table):
# iptables - d在PUT -s xx.xxx.xx.xx -j DROP
# iptables - d在PUT -s 65.55.44.100 -j DROP
# service iptables save

To unblock or enable SSH access, go to the remote server and run the following command:

1. Using IPtables Firewall

   # iptables -I INPUT -s 192.168.1.100/24 -p tcp --dport ssh -j ACCEPT

2. Using FirewallD

   firewall-cmd --direct --add-rule ipv4 filter INPUT 1 -m tcp --source 192.168.1.100 -p tcp --dport 22 -j ACCEPT

To unblock ftp access

1. iptables -I INPUT -s 192.168.1.100 -p tcp --dport 20,21 -j ACCEPT or

2. firewall-cmd --direct --add-rule ipv4 filter INPUT 1 -m tcp --source 192.168.1.100 -p tcp --dport 20,21 -j ACCEPT

Try it out!