Connection Unstable

If you're experiencing unstable connections, most of the times (90% of the cases) a firewall issue, ufw, iptables or some configuration on your server or between your Coolify instance (or Coolify Cloud) and your server.

Symptoms

• Server is sometimes reachable, sometimes not.
• You receive a lot of failed connection lost emails.

Diagnosis

• Check your UFW rules with ufw status numbered and see if you have a LIMIT rule for port 22.
• Check your iptables rules with iptables -L -v -n and see if you have a LIMIT rule for port 22.
• Check your server logs (/var/log/ufw.log, /var/log/iptables.log, /var/log/auth.log, /var/log/kern.log) for any firewall related errors.

Solution

• UFW

  • ufw status numbered - if you have port 22 open, but with a LIMIT rule, this is the problem.
  • ufw delete <rule_number> - delete the rule - you probably have IPV4 and IPV6 rules, so you need to delete both.
    • After you deleted the rule, you need to check the status with ufw status numbered and see that the rule is deleted and which rule number is next.
  • ufw allow 22/tcp - add the rule without a limit.

  OR

  • ufw limit 22/tcp 100/minute - add a higher limit.

In case of Coolify Cloud, you can enable connection from Coolify Cloud IP addresses by adding the following to the UFW rules for each IP:

# For each IPv4 address
ufw allow from <ipv4> to any port 22

# For each IPv6 subnet
ufw allow from <ipv6> to any port 22

You can find the current Coolify Cloud IP addresses at https://coolify.io/ipv4.txt and https://coolify.io/ipv6.txt