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The main content of this article is to explain "Why the Linux CentOS firewall opened the designated port but still can not access", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "Why the Linux CentOS firewall opens the designated port but still can't access it"!

The firewall rules are as follows

# Generated by iptables-save v1.4.7 on Tue Aug 20 10:09:45 2019*filter:INPUT ACCEPT [0:0]: FORWARD ACCEPT [0:0]: OUTPUT ACCEPT [192019*filter:INPUT ACCEPT 1438]-An INPUT-m state-state RELATED ESTABLISHED-j ACCEPT-An INPUT-p icmp- j ACCEPT-An INPUT-I lo-j ACCEPT-An INPUT-p tcp-m state-state NEW-m tcp-dport 22-j ACCEPT-An INPUT-p tcp-m tcp-- dport 20001-j ACCEPT-An INPUT-j REJECT-- reject-with icmp-host-prohibited-A FORWARD-j REJECT-- reject-with icmp-host-prohibitedCOMMIT# Completed on Tue Aug 20 10:09:45 2019

Notice this line-An INPUT-j REJECT-- reject-with icmp-host-prohibited. If the rule we add is below this line, then it will not take effect.

Solution: add our rules before-An INPUT-j REJECT-reject-with icmp-host-prohibited

At this point, I believe you have a deeper understanding of "why the Linux CentOS firewall opened the designated port or can not access", might as well to the actual operation of it! Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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