CentOS 7系统下无法停用iptables的问题求助

Hey Ethan, let's walk through how to fully disable all Linux-level firewalls on your CentOS 7 server and ensure all ports/protocols stay open—no more unexpected disconnections.

First, let's clear up a common confusion on CentOS 7: the default firewall service is firewalld, not the traditional iptables service you were trying to stop. That's why your initial systemctl stop iptables commands didn't do anything—probably the iptables service wasn't even running!

Here's the step-by-step fix, safe to run (just keep your VNC access handy in case anything goes wrong, though these steps shouldn't cause issues):

1. Check which firewall services are active #

First confirm what's running on your server:

systemctl status firewalld
systemctl status iptables
systemctl status ip6tables

You'll likely see firewalld is active, while iptables/ip6tables are inactive or not installed.

2. Stop and disable firewalld (the main culprit) #

Stop the service immediately, disable it from starting on boot, and "mask" it to prevent accidental re-enabling:

systemctl stop firewalld
systemctl disable firewalld
systemctl mask firewalld

3. Handle traditional iptables/ip6tables services (if they exist) #

If you had the iptables-services package installed, stop and disable those too:

# For IPv4
systemctl stop iptables
systemctl disable iptables
systemctl mask iptables

# For IPv6 (don't skip this!)
systemctl stop ip6tables
systemctl disable ip6tables
systemctl mask ip6tables

4. Reset iptables rules to allow all traffic (safe way) #

Your earlier iptables -F caused a disconnect because your server's default INPUT policy was set to DROP—clearing rules removed the exception that allowed SSH access. To avoid this, first set all chain policies to ACCEPT, then clear rules:

# IPv4
iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT
iptables -F  # Flush all rules
iptables -X  # Delete custom chains

# IPv6 (do this too to cover all protocols)
ip6tables -P INPUT ACCEPT
ip6tables -P FORWARD ACCEPT
ip6tables -P OUTPUT ACCEPT
ip6tables -F
ip6tables -X

5. Save the rules to persist after reboot #

Even though we disabled the firewall services, saving these open rules ensures nothing reverts unexpectedly:

iptables-save > /etc/sysconfig/iptables
ip6tables-save > /etc/sysconfig/ip6tables

6. Verify everything is working #

Check your current iptables rules to confirm all traffic is allowed:

iptables -L -n
ip6tables -L -n

You should see all chains have a default policy of ACCEPT and no restrictive rules listed. Now test from outside: ping the server, connect via SSH, and load your website—all should work normally.

To recap why your earlier attempts failed:

• systemctl stop iptables didn't work because CentOS 7 uses firewalld by default, not the legacy iptables service.
• iptables -F disconnected you because the default INPUT policy was DROP—without any allow rules left, external connections were blocked. Setting the default policy to ACCEPT first fixes this.

备注：内容来源于stack exchange，提问作者Ethan_m