Avoid firewall conflicts

Avoid firewall conflicts in the following Linux distributions:

Linux distribution


SUSE Linux Enterprise Server 12 SP2

Installations have the FW_LO_NOTRACK flag turned on by default in the openSUSE firewall. It speeds up packet processing on the loopback interface but breaks certain firewall setups that redirect outgoing packets via custom rules on the local machine.

To turn off the FW_LO_NOTRACK option:

  1. In /etc/sysconfig/SuSEfirewall2, set FW_LO_NOTRACK="no".

  2. Either restart the firewall or reboot the system.

SUSE Linux Enterprise Server 12 SP3

No change is required, as installations have the FW_LO_NOTRACK flag turned off by default.

Red Hat Enterprise Linux (RHEL) 8

Configure the FirewallBackend option:

  1. Verify that firewalld is running.

  2. In /etc/firewalld/firewalld.conf, set FirewallBackend=iptables (formerly FirewallBackend=nftables).

Alternatively, to allow traffic to enter the default bridge network (docker0), run the following commands:

firewall-cmd --permanent --zone=trusted --add-interface=docker0
firewall-cmd --reload